Since the Sixth Book has described the iron tools,
the vessels and the machines used in mines, this
Book will describe the methods of assaying 1 ores;
because it is desirable to first test them in order
that the material mined may be advantageously
smelted, or that the dross may be purged away and
the metal made pure. Although writers have men−
tioned such tests, yet none of them have set down the
directions for performing them, wherefore it is no
wonder that those who come later have written nothing on the subject.
By tests of this kind miners can determine with certainty whether
ores contain any metal in them or not; or if it has already been
indicated that the ore contains one or more metals, the tests show whether
it is much or little; the miners also ascertain by such tests the method by
which the metal can be separated from that part of the ore devoid of it;
and further, by these tests, they determine that part in which there is much
metal from that part in which there is little. Unless these tests have been
carefully applied before the metals are melted out, the ore cannot be smelted
without great loss to the owners, for the parts which do not easily melt in the
fire carry the metals off with them or consume them. In the last case, they pass
off with the fumes; in the other case they are mixed with the slag and furnace
accretions, and in such event the owners lose the labour which they have spent
in preparing the furnaces and the crucibles, and further, it is necessary for them
to incur fresh expenditure for fluxes and other things. Metals, when they have
been melted out, are usually assayed in order that we may ascertain what pro−
portion of silver is in a centumpondium of copper or lead, or what quantity of
gold is in one libra of silver; and, on the other hand, what proportion of copper
or lead is contained in a centumpondium of silver, or what quantity of silver is
contained in one libra of gold. And from this we can calculate whether it
will be worth while to separate the precious metals from the base metals, or
not. Further, a test of this kind shows whether coins are good or are
debased; and readily detects silver, if the coiners have mixed more than is
lawful with the gold; or copper, if the coiners have alloyed with the gold or
silver more of it than is allowable. I will explain all these methods with the
utmost care that I can.
The method of assaying ore used by mining people, differs from
smelting only by the small amount of material used. Inasmuch as, by
smelting a small quantity, they learn whether the smelting of a large
quantity will compensate them for their expenditure; hence, if they are not
particular to employ assays, they may, as I have already said, sometimes smelt
the metal from the ore with a loss or sometimes without any profit; for they
can assay the ore at a very small expense, and smelt it only at a great
expense. Both processes, however, are carried out in the same way, for just
as we assay ore in a little furnace, so do we smelt it in the large furnace. Also
in both cases charcoal and not wood is burned. Moreover, in the crucible
when metals are tested, be they gold, silver, copper, or lead, they are mixed in
precisely the same way as they are mixed in the blast furnace when they
are smelted. Further, those who assay ores with fire, either pour out the
metal in a liquid state, or, when it has cooled, break the crucible and clean
the metal from slag; and in the same way the smelter, as soon as the metal
flows from the furnace into the forehearth, pours in cold water and takes the
slag from the metal with a hooked bar. Finally, in the same way that gold
and silver are separated from lead in a cupel, so also are they separated in
the cupellation furnace.
It is necessary that the assayer who is testing ore or metals should be
prepared and instructed in all things necessary in assaying, and that he
should close the doors of the room in which the assay furnace stands, lest
ROUND ASSAY FURNACE.
RECTANGULAR ASSAY FURNACE.
anyone coming at an inopportune moment might disturb his thoughts when
they are intent on the work. It is also necessary for him to place his balances
in a case, so that when he weighs the little buttons of metal the scales may
not be agitated by a draught of air, for that is a hindrance to his work.
Now I will describe the different things which are necessary in assaying,
beginning with the assay furnace, of which one differs from another in
shape, material, and the place in which it is set. In shape, they may be
round or rectangular, the latter shape being more suited to assaying ores.
The materials of the assay furnaces differ, in that one is made of bricks,
another of iron, and certain ones of clay. The one of bricks is built on a
chimney−hearth which is three and a half feet high; the iron one is placed
in the same position, and also the one of clay. The brick one is a cubit high,
a foot wide on the inside, and one foot two digits long; at a point five digits
above the hearthwhich is usually the thickness of an unbaked 2 brick
an iron plate is laid, and smeared over with lute on the upper side to prevent
it from being injured by the fire; in front of the furnace above the plate is a
mouth a palm high, five digits wide, and rounded at the top. The iron plate
AOPENINGS IN THE PLATE. BPART OF PLATE WHICH PROJECTS BEYOND THE FURNACE.
has three openings which are one digit wide and three digits long, one is at
each side and the third at the back; through them sometimes the ash falls
from the burning charcoal, and sometimes the draught blows through the
chamber which is below the iron plate, and stimulates the fire. For this
reason this furnace when used by metallurgists is named from assaying, but
when used by the alchemists it is named from the wind 3 . The part of the
iron plate which projects from the furnace is generally three−quarters of a
palm long and a palm wide; small pieces of charcoal, after being laid thereon,
can be placed quickly in the furnace through its mouth with a pair of tongs,
or again, if necessary, can be taken out of the furnace and laid there.
The iron assay furnace is made of four iron bars a foot and a half high,
which at the bottom are bent outward and broadened a short distance to enable
them to stand more firmly; the front part of the furnace is made from two
of these bars, and the back part from two of them; to these bars on both
sides are joined and welded three iron cross−bars, the first at a height of a palm
from the bottom, the second at a height of a foot, and the third at the top.
The upright bars are perforated at that point where the side cross−bars are
joined to them, in order that three similar iron bars on the remaining sides
can be engaged in them; thus there are twelve cross−bars, which make
three stages at unequal intervals. At the lower stage, the upright bars are
distant from each other one foot and five digits; and at the middle stage the
front is distant from the back three palms and one digit, and the sides are
distant from each other three palms and as many digits; at the highest stage
from the front to the back there is a distance of two palms, and between the
sides three palms, so that in this way the furnace becomes narrower at the
top. Furthermore, an iron rod, bent to the shape of the mouth, is set into
the lowest bar of the front; this mouth, just like that of the brick furnace,
is a palm high and five digits wide. Then the front cross−bar of the lower
stage is perforated on each side of the mouth, and likewise the back one;
through these perforations there pass two iron rods, thus making altogether
four bars in the lower stage, and these support an iron plate smeared with
lute; part of this plate also projects outside the furnace. The outside of
the furnace from the lower stage to the upper, is covered with iron plates,
which are bound to the bars by iron wires, and smeared with lute to enable
them to bear the heat of the fire as long as possible.
As for the clay furnace, it must be made of fat, thick clay, medium so
far as relates to its softness or hardness. This furnace has exactly the same
height as the iron one, and its base is made of two earthenware tiles, one
foot and three palms long and one foot and one palm wide. Each side of the
fore part of both tiles is gradually cut away for the length of a palm, so
that they are half a foot and a digit wide, which part projects from the
furnace; the tiles are about a digit and a half thick. The walls are similarly
of clay, and are set on the lower tiles at a distance of a digit from the edge,
and support the upper tiles; the walls are three digits high and have four
openings, each of which is about three digits high; those of the back part and
of each side are five digits wide, and of the front, a palm and a half wide, to
enable the freshly made cupels to be conveniently placed on the hearth, when
it has been thoroughly warmed, that they may be dried there. Both tiles
are bound on the outer edge with iron wire, pressed into them, so that they
will be less easily broken; and the tiles, not unlike the iron bed−plate, have
three openings three digits long and a digit wide, in order that when the upper
one on account of the heat of the fire or for some other reason has become
damaged, the lower one may be exchanged and take its place. Through these
holes, the ashes from the burning charcoal, as I have stated, fall down, and
air blows into the furnace after passing through the openings in the walls of
the chamber. The furnace is rectangular, and inside at the lower part it is
three palms and one digit wide and three palms and as many digits long. At
the upper part it is two palms and three digits wide, so that it also grows
narrower; it is one foot high; in the middle of the back it is cut out at
the bottom in the shape of a semicircle, of half a digit radius. Not
unlike the furnace before described, it has in its forepart a mouth which is
rounded at the top, one palm high and a palm and a digit wide. Its door
is also made of clay, and this has a window and a handle; even the lid
of the furnace which is made of clay has its own handle, fastened on with iron
wire. The outer parts and sides of this furnace are bound with iron wires,
which are usually pressed in, in the shape of triangles. The brick furnaces
must remain stationary; the clay and iron ones can be carried from one
place to another. Those of brick can be prepared more quickly, while those
of iron are more lasting, and those of clay are more suitable. Assayers
also make temporary furnaces in another way; they stand three bricks
on a hearth, one on each side and a third one at the back, the fore−part lies
open to the draught, and on these bricks is placed an iron plate, upon which
they again stand three bricks, which hold and retain the charcoal.
The setting of one furnace differs from another, in that some are placed
higher and others lower; that one is placed higher, in which the man who is
assaying the ore or metals introduces the scorifier through the mouth with the
tongs; that one is placed lower, into which he introduces the crucible
through its open top.
In some cases the assayer uses an iron hoop 4 in place of a furnace;
this is placed upon the hearth of a chimney, the lower edge being daubed
with lute to prevent the blast of the bellows from escaping under it.
If the blast is given slowly, the ore will be smelted and the copper will melt in
the triangular crucible, which is placed in it and taken away again with the
tongs. The hoop is two palms high and half a digit thick; its diameter is
generally one foot and one palm, and where the blast from the bellows enters
into it, it is notched out. The bellows is a double one, such as goldworkers
use, and sometimes smiths. In the middle of the bellows there is a board in
which there is an air−hole, five digits wide and seven long, covered by a
little flap which is fastened over the air−hole on the lower side of the board;
this flap is of equal length and width. The bellows, without its head, is
three feet long, and at the back is one foot and one palm wide and
somewhat rounded, and it is three palms wide at the head; the head itself
is three palms long and two palms and a digit wide at the part where it joins
the boards, then it gradually becomes narrower. The nozzle, of which there
is only one, is one foot and two digits long; this nozzle, and one−half of the
head in which the nozzle is fixed, are placed in an opening of the wall, this
being one foot and one palm thick; it reaches only to the iron hoop on the
hearth, for it does not project beyond the wall. The hide of the bellows is
fixed to the bellows−boards with its own peculiar kind of iron nails. It joins
both bellows−boards to the head, and over it there are cross strips of
hide fixed to the bellows−boards with broad−headed nails, and similarly
fixed to the head. The middle board of the bellows rests on an iron bar,
to which it is fastened with iron nails clinched on both ends, so that it cannot
move; the iron bar is fixed between two upright posts, through which it
penetrates. Higher up on these upright posts there is a wooden axle, with
iron journals which revolve in the holes in the posts. In the middle of
this axle there is mortised a lever, fixed with iron nails to prevent it from
flying out; the lever is five and a half feet long, and its posterior end is
engaged in the iron ring of an iron rod which reaches to the "tail" of the
lowest bellows−board, and there engages another similar ring. And so when
the workman pulls down the lever, the lower part of the bellows is raised and
drives the wind into the nozzle; then the wind, penetrating through the hole
in the middle bellows−board, which is called the air−hole, lifts up the upper
part of the bellows, upon whose upper board is a piece of lead, heavy enough
to press down that part of the bellows again, and this being pressed down
blows a blast through the nozzle. This is the principle of the double bellows,
which is peculiar to the iron hoop where are placed the triangular crucibles in
which copper ore is smelted and copper is melted.
AIRON HOOP. BDOUBLE BELLOWS. CITS NOZZLE. DLEVER.
I have spoken of the furnaces and the iron hoop; I will now speak of
the muffles and the crucibles. The muffle is made of clay, in the shape
of an inverted gutter tile; it covers the scorifiers, lest coal dust fall into
them and interfere with the assay. It is a palm and a half broad, and the
height, which corresponds with the mouth of the furnace, is generally a palm,
and it is nearly as long as the furnace; only at the front end does it touch
the mouth of the furnace, everywhere else on the sides and at the back
there is a space of three digits, to allow the charcoal to lie in the open space
between it and the furnace. The muffle is as thick as a fairly thick earthen
jar; its upper part is entire; the back has two little windows, and each side
has two or three or even four, through which the heat passes into the scorifiers
and melts the ore. In place of little windows, some muffles have small holes,
ten in the back and more on each side. Moreover, in the back below the
little windows, or small holes, there are cut away three semi−circular notches
half a digit high, and on each side there are four. The back of the muffle
is generally a little lower than the front.
ABROAD LITTLE WINDOWS OF MUFFLE. BNARROW ONES. COPENINGS IN THE
The crucibles differ in the materials from which they are made, because
they are made of either clay or ashes; and those of clay, which we also call
"earthen," differ in shape and size. Some are made in the shape of a mod−
erately thick salver (scorifiers), three digits wide, and of a capacity of an
uncía measure; in these the ore mixed with fluxes is melted, and they are used
by those who assay gold or silver ore. Some are triangular and much
thicker and more capacious, holding five, or six, or even more uncíae; in
these copper is melted, so that it can be poured out, expanded, and tested
with fire, and in these copper ore is usually melted.
The cupels are made of ashes; like the preceding scorifiers they are
tray−shaped, and their lower part is very thick but their capacity is less.
In these lead is separated from silver, and by them assays are concluded.
Inasmuch as the assayers themselves make the cupels, something must
be said about the material from which they are made, and the method
of making them. Some make them out of all kinds of ordinary ashes; these
are not good, because ashes of this kind contain a certain amount of fat,
whereby such cupels are easily broken when they are hot. Others make
them likewise out of any kind of ashes which have been previously
leached; of this kind are the ashes into which warm water has been infused
for the purpose of making lye. These ashes, after being dried in the sun or
a furnace, are sifted in a hair sieve; and although warm water washes away the
ASCORIFIER. BTRIANGULAR CRUCIBLE. CCUPEL.
fat from the ashes, still the cupels which are made from such ashes are not
very good because they often contain charcoal dust, sand, and pebbles.
Some make them in the same way out of any kind of ashes, but first of all
pour water into the ashes and remove the scum which floats thereon; then,
after it has become clear, they pour away the water, and dry the ashes; they
then sift them and make the cupels from them. These, indeed, are good,
but not of the best quality, because ashes of this kind are also not devoid of
small pebbles and sand. To enable cupels of the best quality to be made, all
the impurities must be removed from the ashes. These impurities are of
two kinds; the one sort light, to which class belong charcoal dust and fatty
material and other things which float in water, the other sort heavy, such
as small stones, fine sand, and any other materials which settle in the
bottom of a vessel. Therefore, first of all, water should be poured into the
ashes and the light impurities removed; then the ashes should be
kneaded with the hands, so that they will become properly mixed with
the water. When the water has become muddy and turbid, it should be
poured into a second vessel. In this way the small stones and fine sand, or
any other heavy substance which may be there, remain in the first vessel,
and should be thrown away. When all the ashes have settled in this second
vessel, which will be shown if the water has become clear and does not taste
of the flavour of lye, the water should be thrown away, and the ashes
which have settled in the vessel should be dried in the sun or in a furnace.
This material is suitable for the cupels, especially if it is the ash of beech
wood or other wood which has a small annual growth; those ashes made
from twigs and limbs of vines, which have rapid annual growth, are not so
good, for the cupels made from them, since they are not sufficiently dry,
frequently crack and break in the fire and absorb the metals. If ashes of
beech or similar wood are not to be had, the assayer makes little balls of such
ashes as he can get, after they have been cleared of impurities in the manner
before described, and puts them in a baker' s or potter' s oven to burn, and from
these the cupels are made, because the fire consumes whatever fat or damp
there may be. As to all kinds of ashes, the older they are the better, for it is
necessary that they should have the greatest possible dryness. For this
reason ashes obtained from burned bones, especially from the bones of the
heads of animals, are the most suitable for cupels, as are also those ashes
obtained from the horns of deer and the spines of fishes. Lastly, some take the
ashes which are obtained from burnt scrapings of leather, when the tanners
scrape the hides to clear them from hair. Some prefer to use compounds,
that one being recommended which has one and a half parts of ashes from the
bones of animals or the spines of fishes, and one part of beech ashes, and half a
part of ashes of burnt hide scrapings. From this mixture good cupels are
made, though far better ones are obtained from equal portions of ashes of
burnt hide scrapings, ashes of the bones of heads of sheep and calves, and
ashes of deer horns. But the best of all are produced from deer horns alone,
burnt to powder; this kind, by reason of its extreme dryness, absorbs metals
least of all. Assayers of our own day, however, generally make the
cupels from beech ashes. These ashes, after being prepared in the
manner just described, are first of all sprinkled with beer or water, to make
them stick together, and are then ground in a small mortar. They are ground
again after being mixed with the ashes obtained from the skulls of beasts or from
the spines of fishes; the more the ashes are ground the better they are.
Some rub bricks and sprinkle the dust so obtained, after sifting it, into the
beech ashes, for dust of this kind does not allow the hearth−lead to absorb
the gold or silver by eating away the cupels. Others, to guard against the
same thing, moisten the cupels with white of egg after they have been made,
and when they have been dried in the sun, again crush them; especially if they
want to assay in it an ore or copper which contains iron. Some moisten the
ashes again and again with cow' s milk, and dry them, and grind them in a
small mortar, and then mould the cupels. In the works in which silver
is separated from copper, they make cupels from two parts of the ashes of
the crucible of the cupellation furnace, for these ashes are very dry, and from
one part of bone−ash. Cupels which have been made in these ways also
need to be placed in the sun or in a furnace; afterward, in whatever way
they have been made, they must be kept a long time in dry places, for the
older they are, the dryer and better they are.
Not only potters, but also the assayers themselves, make scorifiers
and triangular crucibles. They make them out of fatty clay, which is
dry 5 , and neither hard nor soft. With this clay they mix the dust of old
broken crucibles, or of burnt and worn bricks; then they knead with a
pestle the clay thus mixed with dust, and then dry it. As to these crucibles,
the older they are, the dryer and better they are. The moulds in which the
cupels are moulded are of two kinds, that is, a smaller size and a larger size.
In the smaller ones are made the cupels in which silver or gold is purged
from the lead which has absorbed it; in the larger ones are made cupels in
which silver is separated from copper and lead. Both moulds are made out
of brass and have no bottom, in order that the cupels can be taken out of
them whole. The pestles also are of two kinds, smaller and larger, each
likewise of brass, and from the lower end of them there projects a round
knob, and this alone is pressed into the mould and makes the hollow part of
the cupel. The part which is next to the knob corresponds to the upper
part of the mould.
ALITTLE MOULD. BINVERTED MOULD. CPESTLE. DITS KNOB. ESECOND
So much for these matters. I will now speak of the preparation of the
ore for assaying. It is prepared by roasting, burning, crushing, and wash−
ing. It is necessary to take a fixed weight of ore in order that one may
determine how great a portion of it these preparations consume. The
hard stone containing the metal is burned in order that, when its hardness
has been overcome, it can be crushed and washed; indeed, the very hardest
kind, before it is burned, is sprinkled with vinegar, in order that it may more
rapidly soften in the fire. The soft stone should be broken with a hammer,
crushed in a mortar and reduced to powder; then it should be washed
and then dried again. If earth is mixed with the mineral, it is washed in a
basin, and that which settles is assayed in the fire after it is dried. All mining
products which are washed must again be dried. But ore which is rich in
metal is neither burned nor crushed nor washed, but is roasted, lest that
method of preparation should lose some of the metal. When the fires have
been kindled, this kind of ore is roasted in an enclosed pot, which is stopped
up with lute. A less valuable ore is even burned on a hearth, being placed
upon the charcoal; for we do not make a great expenditure upon metals, if
they are not worth it. However, I will go into fuller details as to all these
methods of preparing ore, both a little later, and in the following Book.
For the present, I have decided to explain those things which mining
people usually call fluxes 6 because they are added to ores, not only for
assaying, but also for smelting. Great power is discovered in all these fluxes,
but we do not see the same effects produced in every case; and some are of a
very complicated nature. For when they have been mixed with the ore
and are melted in either the assay or the smelting furnace, some of them,
because they melt easily, to some extent melt the ore; others, because they
either make the ore very hot or penetrate into it, greatly assist the fire in
separating the impurities from the metals, and they also mix the fused part
with the lead, or they partly protect from the fire the ore whose metal contents
would be either consumed in the fire, or carried up with the fumes and fly out
of the furnace; some fluxes absorb the metals. To the first order be−
longs lead, whether it be reduced to little granules or resolved into ash by
fire, or red−lead 7 , or ochre made from lead 8 , or litharge, or hearth−lead, or
galena; also copper, the same either roasted or in leaves or filings 9 ; also the
slags of gold, silver, copper, and lead; also soda 10 , its slags, saltpetre, burned
alum, vitriol, sal tostus, and melted salt 11 ; stones which easily melt
in hot furnaces, the sand which is made from them 12 ; soft tophus 13 ,
and a certain white schist 14 . But lead, its ashes, red−lead, ochre, and
litharge, are more efficacious for ores which melt easily; hearth−lead for
those which melt with difficulty; and galena for those which melt with
greater difficulty. To the second order belong iron filings, their slag, sal
artificíosus, argol, dried lees of vinegar 15 , and the lees of the aqua which separates
gold from silver 16 ; these lees and sal artíficíosus have the power of penetrating
into ore, the argol to a considerable degree, the lees of vinegar to a greater
degree, but most of all those of the aqua which separates gold from silver;
filings and slags of iron, since they melt more slowly, have the power of heat−
ing the ore. To the third order belong pyrites, the cakes which are melted
from them, soda, its slags, salt, iron, iron scales, iron filings, iron slags, vitriol,
the sand which is resolved from stones which easily melt in the fire, and
tophus; but first of all are pyrites and the cakes which are melted from it, for
they absorb the metals of the ore and guard them from the fire which con−
sumes them. To the fourth order belong lead and copper, and their relations.
And so with regard to fluxes, it is manifest that some are natural, others
fall in the category of slags, and the rest are purged from slag. When we
assay ores, we can without great expense add to them a small portion of any
sort of flux, but when we smelt them we cannot add a large portion without
great expense. We must, therefore, consider how great the cost is, to avoid
incurring a greater expense on smelting an ore than the profit we make out of
the metals which it yields.
The colour of the fumes which the ore emits after being placed on a hot
shovel or an iron plate, indicates what flux is needed in addition to the lead,
for the purpose of either assaying or smelting. If the fumes have a purple
tint, it is best of all, and the ore does not generally require any flux whatever.
If the fumes are blue, there should be added cakes melted out of pyrites or
other cupriferous rock; if yellow, litharge and sulphur should be added; if
red, glass−galls 17 and salt; if green, then cakes melted from cupriferous stones,
litharge, and glass−galls; if the fumes are black, melted salt or iron slag,
litharge and white lime rock. If they are white, sulphur and iron which is
eaten with rust; if they are white with green patches, iron slag and
sand obtained from stones which easily melt; if the middle part of the
fumes are yellow and thick, but the outer parts green, the same sand and
iron slag. The colour of the fumes not only gives us information as to the
proper remedies which should be applied to each ore, but also more or less
indication as to the solidified juices which are mixed with it, and which give
forth such fumes. Generally, blue fumes signify that the ore contains azure;
yellow, orpiment; red, realgar; green, chrysocolla; black, black bitumen;
white, tin 18 ; white with green patches, the same mixed with chrysocolla;
the middle part yellow and other parts green show that it contains sulphur.
Earth, however, and other things dug up which contain metals, some−
times emit similarly coloured fumes.
If the ore contains any stíbíum, then iron slag is added to it; if pyrites,
then are added cakes melted from a cupriferous stone and sand made from
stones which easily melt. If the ore contains iron, then pyrites and sulphur
are added; for just as iron slag is the flux for an ore mixed with sulphur, so
on the contrary, to a gold or silver ore containing iron, from which they are
not easily separated, is added sulphur and sand made from stones which
Sal artíficíosus 19 suitable for use in assaying ore is made in many ways.
By the first method, equal portions of argol, lees of vinegar, and urine,
are all boiled down together till turned into salt. The second method is from
equal portions of the ashes which wool−dyers use, of lime. of argol purified,
and of melted salt; one libra of each of these ingredients is thrown into
twenty líbrae of urine; then all are boiled down to one−third and strained,
and afterward there is added to what remains one líbra and four uncíae
of unmelted salt, eight pounds of lye being at the same time poured into
the pots, with litharge smeared around on the inside, and the whole is boiled
till the salt becomes thoroughly dry. The third method follows. Unmelted
salt, and iron which is eaten with rust, are put into a vessel, and after
urine has been poured in, it is covered with a lid and put in a warm place
for thirty days; then the iron is washed in the urine and taken out, and
the residue is boiled until it is turned into salt. In the fourth method by
which sal artíficíosus is prepared, the lye made from equal portions of
lime and the ashes which wool−dyers use, together with equal portions of
salt, soap, white argol, and saltpetre, are boiled until in the end the mix−
ture evaporates and becomes salt. This salt is mixed with the concentrates
from washing, to melt them.
Saltpetre is prepared in the following manner, in order that it may be
suitable for use in assaying ore. It is placed in a pot which is smeared on
the inside with litharge, and lye made of quicklime is repeatedly poured over
it, and it is heated until the fire consumes it. Wherefore the saltpetre
does not kindle with the fire, since it has absorbed the lime which preserves
it, and thus it is prepared 20 .
The following compositions 21 are recommended to smelt all ores which
the heat of fire breaks up or melts only with difficulty. Of these, one is made
from stones of the third order, which easily melt when thrown into hot
furnaces. They are crushed into pure white powder, and with half an uncia
of this powder there are mixed two unciae of yellow litharge, likewise crushed.
This mixture is put into a scorifier large enough to hold it, and placed under
the muffle of a hot furnace; when the charge flows like water, which occurs
after half an hour, it is taken out of the furnace and poured on to a stone,
and when it has hardened it has the appearance of glass, and this is likewise
crushed. This powder is sprinkled over any metalliferous ore which does
not easily melt when we are assaying it, and it causes the slag to exude.
Others, in place of litharge, substitute lead ash, 22 which is made in the
following way: sulphur is thrown into lead which has been melted in a
crucible, and it soon becomes covered with a sort of scum; when this is
removed, sulphur is again thrown in, and the skin which forms is again taken
off; this is frequently repeated, in fact until all the lead is turned into
powder. There is a powerful flux compound which is made from one uncía
each of prepared saltpetre, melted salt, glass−gall, and argol, and one−third
of an uncia of litharge and a bes of glass ground to powder; this flux, being
added to an equal weight of ore, liquefies it. A more powerful flux is made by
placing together in a pot, smeared on the inside with litharge, equal portions
of white argol, common salt, and prepared saltpetre, and these are heated
until a white powder is obtained from them, and this is mixed with as much
litharge; one part of this compound is mixed with two parts of the ore which
is to be assayed. A still more powerful flux than this is made out of ashes
of black lead, saltpetre, orpiment, stíbíum, and dried lees of the aqua with
which gold workers separate gold from silver. The ashes of lead 23 are made from
one pound of lead and one pound of sulphur; the lead is flattened out into
sheets by pounding with a hammer, and placed alternately with sulphur in a
crucible or pot, and they are heated together until the fire consumes the
sulphur and the lead turns to ashes. One líbra of crushed saltpetre is mixed
with one libra of orpiment similarly ground to powder, and the two are cooked
in an iron pan until they liquefy; they are then poured out, and after cool−
ing are again ground to powder. A líbra of stíbíum and a bes of the
dried lees ( of what? ) are placed alternately in a crucible and heated to the
point at which they form a button, which is similarly reduced to powder.
A bes of this powder and one líbra of the ashes of lead, as well as a líbra of
powder made out of the saltpetre and orpiment, are mixed together and a
powder is made from them, one part of which added to two parts of ore
liquefies it and cleanses it of dross. But the most powerful flux is one which
has two drachmae of sulphur and as much glass−galls, and half an uncía of each of
the following, stíbíum, salt obtained from boiled urine, melted common salt,
prepared saltpetre, litharge, vitriol, argol, salt obtained from ashes of musk ivy,
dried lees of the aqua by which gold−workers separate gold from silver,
alum reduced by fire to powder, and one uncía of camphor 24 combined with
sulphur and ground into powder. A half or whole portion of this mixture,
as the necessity of the case requires, is mixed with one portion of the ore
and two portions of lead, and put in a scorifier; it is sprinkled with powder
of crushed Venetian glass, and when the mixture has been heated for an hour
and a half or two hours, a button will settle in the bottom of the scorifier, and
from it the lead is soon separated.
There is also a flux which separates sulphur, orpiment and realgar from
metalliferous ore. This flux is composed of equal portions of iron slag,
white tophus, and salt. After these juices have been secreted, the ores
themselves are melted, with argol added to them. There is one flux which
preserves stíbíum from the fire, that the fire may not consume it, and
which preserves the metals from the stíbíum; and this is composed of equal
portions of sulphur, prepared saltpetre, melted salt, and vitriol, heated
together in lye until no odour emanates from the sulphur, which occurs after
a space of three or four hours. 25
It is also worth while to substitute certain other mixtures. Take two
portions of ore properly prepared, one portion of iron filings, and likewise
one portion of salt, and mix; then put them into a scorifier and place them
in a muffle furnace; when they are reduced by the fire and run together, a
button will settle in the bottom of the scorifier. Or else take equal portions
of ore and of lead ochre, and mix with them a small quantity of iron filings,
and put them into a scorifier, then scatter iron filings over the mixture. Or
else take ore which has been ground to powder and sprinkle it in a crucible,
and then sprinkle over it an equal quantity of salt that has been three or
four times moistened with urine and dried; then, again and again alternately,
powdered ore and salt; next, after the crucible has been covered with a
lid and sealed, it is placed upon burning charcoal. Or else take one portion of
ore, one portion of minute lead granules, half a portion of Venetian glass,
and the same quantity of glass−galls. Or else take one portion of ore, one
portion of lead granules, half a portion of salt, one−fourth of a portion of argol,
and the same quantity of lees of the aqua which separates gold from silver.
Or else take equal portions of prepared ore and a powder in which there
are equal portions of very minute lead granules, melted salt, stíbíum and
iron slag Or else take equal portions of gold ore, vitriol, argol, and of salt.
So much for the fluxes.
In the assay furnace, when it has been prepared in the way in which I
have described, is first placed a muffle. Then selected pieces of live charcoals
are laid on it, for, from pieces of inferior quality, a great quantity of ash collects
around the muffle and hinders the action of the fire. Then the scorifiers are
placed under the muffle with tongs, and glowing coals are placed under the
fore part of the muffle to warm the scorifiers more quickly; and when the lead
or ore is to be placed in the scorifiers, they are taken out again with the
tongs. When the scorifiers glow in the heat, first of all the ash or small
charcoals, if any have fallen into them, should be blown away with an iron
pipe two feet long and a digit in diameter; this same thing must be done
if ash or small coal has fallen into the cupels. Next, put in a small ball of lead
with the tongs, and when this lead has begun to be turned into fumes and
consumed, add to it the prepared ore wrapped in paper. It is preferable that
the assayer should wrap it in paper, and in this way put it in the scorifier,
than that he should drop it in with a copper ladle; for when the
scorifiers are small, if he uses a ladle he frequently spills some part of the
ore. When the paper is burnt, he stirs the ore with a small charcoal held in
the tongs, so that the lead may absorb the metal which is mixed in the ore;
when this mixture has taken place, the slag partly adheres by its cir−
cumference to the scorifier and makes a kind of black ring, and partly
floats on the lead in which is mixed the gold or silver; then the slag must
be removed from it.
The lead used must be entirely free from every trace of silver, as is that
which is known as Víllacense. 26 But if this kind is not obtainable, the lead
must be assayed separately, to determine with certainty that proportion of
silver it contains, so that it may be deducted from the calculation of the
ore, and the result be exact; for unless such lead be used, the assay will be
false and misleading. The lead balls are made with a pair of iron tongs,
about one foot long; its iron claws are so formed that when pressed
together they are egg−shaped; each claw contains a hollow cup, and when
the claws are closed there extends upward from the cup a passage, so there
are two openings, one of which leads to each hollow cup. And so when the
molten lead is poured in through the openings, it flows down into the hollow
cup, and two balls are formed by one pouring.
In this place I ought not to omit mention of another method of assaying
employed by some assayers. They first of all place prepared ore in the
scorifiers and heat it, and afterward they add the lead. Of this method I
cannot approve, for in this way the ore frequently becomes cemented, and
for this reason it does not stir easily afterward, and is very slow in mixing
with the lead.
If the whole space of the furnace covered by the muffle is not filled with
scorifiers, cupels are put in the empty space, in order that they may become
warmed in the meantime. Sometimes, however, it is filled with scorifiers,
when we are assaying many different ores, or many portions of one ore at the
same time. Although the cupels are usually dried in one hour, yet smaller
ones are done more quickly, and the larger ones more slowly. Unless the
cupels are heated before the metal mixed with lead is placed in them, they
ACLAWS OF THE TONGS. BIRON, GIVING FORM OF AN EGG. COPENING.
frequently break, and the lead always sputters and sometimes leaps out of them;
if the cupel is broken or the lead leaps out of it, it is necessary to assay
another portion of ore; but if the lead only sputters, then the cupels should
be covered with broad thin pieces of glowing charcoal, and when the lead
strikes these, it falls back again, and thus the mixture is slowly exhaled.
Further, if in the cupellation the lead which is in the mixture is not con−
sumed, but remains fixed and set, and is covered by a kind of skin, this is a
sign that it has not been heated by a sufficiently hot fire; put into the
mixture, therefore, a dry pine stick, or a twig of a similar tree, and hold it
in the hand in order that it can be drawn away when it has been heated.
Then take care that the heat is sufficient and equal; if the heat has not
passed all round the charge, as it should when everything is done rightly,
but causes it to have a lengthened shape, so that it appears to have a tail,
this is a sign that the heat is deficient where the tail lies. Then in order
that the cupel may be equally heated by the fire, turn it around with a small
iron hook, whose handle is likewise made of iron and is a foot and a half long.
SMALL IRON HOOK.
Next, if the mixture has not enough lead, add as much of it as is required
with the iron tongs, or with the brass ladle to which is fastened a very long
handle. In order that the charge may not be cooled, warm the lead beforehand.
But it is better at first to add as much lead as is required to the ore which
needs melting, rather than afterward when the melting has been half finished,
that the whole quantity may not vanish in fumes, but part of it remain
fast. When the heat of the fire has nearly consumed the lead, then is the
time when the gold and silver gleam in their varied colours, and when all the
lead has been consumed the gold or silver settles in the cupel. Then as
soon as possible remove the cupel out of the furnace, and take the button out
of it while it is still warm, in order that it does not adhere to the ashes. This
generally happens if the button is already cold when it is taken out. If the
ashes do adhere to it, do not scrape it with a knife, lest some of it be lost and
the assay be erroneous, but squeeze it with the iron tongs, so that the ashes
drop off through the pressure. Finally, it is of advantage to make two or
three assays of the same ore at the same time, in order that if by chance
one is not successful, the second, or in any event the third, may be certain.
While the assayer is assaying the ore, in order to prevent the great heat
of the fire from injuring his eyes, it will be useful for him always to have
ready a thin wooden tablet, two palms wide, with a handle by which it may
be held, and with a slit down the middle in order that he may look through
it as through a crack, since it is necessary for him to look frequently within
and carefully to consider everything.
AHANDLE OF TABLET. BITS CRACK.
Now the lead which has absorbed the silver from a metallic ore is con−
sumed in the cupel by the heat in the space of three quarters of an hour. When
the assays are completed the muffle is taken out of the furnace, and the
ashes removed with an iron shovel, not only from the brick and iron furnaces,
but also from the earthen one, so that the furnace need not be removed from
From ore placed in the triangular crucible a button is melted out, from
which metal is afterward made. First of all, glowing charcoal is put into
the iron hoop, then is put in the triangular crucible, which contains the ore
together with those things which can liquefy it and purge it of its dross;
then the fire is blown with the double bellows, and the ore is heated until
the button settles in the bottom of the crucible. We have explained that
there are two methods of assaying ore,one, by which the lead is mixed
with ore in the scorifier and afterward again separated from it in the cupel;
the other, by which it is first melted in the triangular earthen crucible and
afterward mixed with lead in the scorifier, and later separated from it in the
cupel. Now let us consider which is more suitable for each ore, or, if neither
is suitable, by what other method in one way or another we can assay it.
We justly begin with a gold ore, which we assay by both methods, for
if it is rich and seems not to be strongly resistant to fire, but to liquefy easily,
one centumpondium of it (known to us as the lesser weights), 27 together with
one and a half, or two unciae of lead of the larger weights, are mixed together
and placed in the scorifier, and the two are heated in the fire until they are
well mixed. But since such an ore sometimes resists melting, add a little
salt to it, either sal torrefactus or sal artificiosus, for this will subdue it, and
prevent the alloy from collecting much dross; stir it frequently with an iron
rod, in order that the lead may flow around the gold on every side, and absorb
it and cast out the waste. When this has been done, take out the alloy and
cleanse it of slag; then place it in the cupel and heat it until it exhales all
the lead, and a bead of gold settles in the bottom.
If the gold ore is seen not to be easily melted in the fire, roast it and
extinguish it with brine. Do this again and again, for the more often you
roast it and extinguish it, the more easily the ore can be crushed fine, and the
more quickly does it melt in the fire and give up whatever dross it possesses.
Mix one part of this ore, when it has been roasted, crushed, and washed, with
three parts of some powder compound which melts ore, and six parts of lead.
Put the charge into the triangular crucible, place it in the iron hoop to which
the double bellows reaches, and heat first in a slow fire, and afterward
gradually in a fiercer fire, till it melts and flows like water. If the ore does
not melt, add to it a little more of these fluxes, mixed with an equal portion
of yellow litharge, and stir it with a hot iron rod until it all melts. Then
take the crucible out of the hoop, shake off the button when it has cooled,
and when it has been cleansed, melt first in the scorifier and afterward in
the cupel. Finally, rub the gold which has settled in the bottom of the cupel,
after it has been taken out and cooled, on the touchstone, in order to find out
what proportion of silver it contains. Another method is to put a centum−
pondium (of the lesser weights) of gold ore into the triangular crucible, and
add to it a drachma (of the larger weights) of glass−galls. If it resists melting,
add half a drachma of roasted argol, and if even then it resists, add the
same quantity of roasted lees of vinegar, or lees of the aqua which separates
gold from silver, and the button will settle in the bottom of the crucible.
Melt this button again in the scorifier and a third time in the cupel.
We determine in the following way, before it is melted in the muffle
furnace, whether pyrites contains gold in it or not: if, after being three times
roasted and three times quenched in sharp vinegar, it has not broken nor
changed its colour, there is gold in it. The vinegar by which it is quenched
should be mixed with salt that is put in it, and frequently stirred and dissolved
for three days. Nor is pyrites devoid of gold, when, after being roasted and
then rubbed on the touchstone, it colours the touchstone in the same way that
it coloured it when rubbed in its crude state. Nor is gold lacking in that,
whose concentrates from washing, when heated in the fire, easily melt, giving
forth little smell and remaining bright; such concentrates are heated in the
fire in a hollowed piece of charcoal covered over with another charcoal.
We also assay gold ore without fire, but more often its sand or the con−
centrates which have been made by washing, or the dust gathered up by
some other means. A little of it is slightly moistened with water and heated
until it begins to exhale an odour, and then to one portion of ore are placed
two portions of quicksilver 28 in a wooden dish as deep as a basin. They are
mixed together with a little brine, and are then ground with a wooden pestle
for the space of two hours, until the mixture becomes of the thickness of dough,
and the quicksilver can no longer be distinguished from the concentrates
made by the washing, nor the concentrates from the quicksilver. Warm, or
at least tepid, water is poured into the dish and the material is washed until
the water runs out clear. Afterward cold water is poured into the same dish,
and soon the quicksilver, which has absorbed all the gold, runs together
into a separate place away from the rest of the concentrates made by
washing. The quicksilver is afterward separated from the gold by means
of a pot covered with soft leather, or with canvas made of woven
threads of cotton; the amalgam is poured into the middle of the cloth or
leather, which sags about one hand' s breadth; next, the leather is folded
over and tied with a waxed string, and the dish catches the quicksilver
which is squeezed through it. As for the gold which remains in the leather,
it is placed in a scorifier and purified by being placed near glowing coals. Others
do not wash away the dirt with warm water, but with strong lye and vinegar,
for they pour these liquids into the pot, and also throw into it the quicksilver
mixed with the concentrates made by washing. Then they set the pot in a
warm place, and after twenty−four hours pour out the liquids with the dirt, and
separate the quicksilver from the gold in the manner which I have described.
Then they pour urine into a jar set in the ground, and in the jar place a
pot with holes in the bottom, and in the pot they place the gold; then the
lid is put on and cemented, and it is joined with the jar; they afterward heat
it till the pot glows red. After it has cooled, if there is copper in the gold
they melt it with lead in a cupel, that the copper may be separated from it;
but if there is silver in the gold they separate them by means of the aqua
which has the power of parting these two metals. There are some who,
when they separate gold from quicksilver, do not pour the amalgam into
a leather, but put it into a gourd−shaped earthen vessel, which they place
in the furnace and heat gradually over burning charcoal; next, with an iron
plate, they cover the opening of the operculum, which exudes vapour, and as
soon as it has ceased to exude, they smear it with lute and heat it for a short
time; then they remove the operculum from the pot, and wipe off the
quicksilver which adheres to it with a hare' s foot, and preserve it for future
use. By the latter method, a greater quantity of quicksilver is lost, and by
the former method, a smaller quantity.
If an ore is rich in silver, as is rudis silver 29 , frequently silver glance,
or rarely ruby silver, gray silver, black silver, brown silver, or yellow silver,
as soon as it is cleansed and heated, a centumpondíum (of the lesser weights) of
it is placed in an uncia of molten lead in a cupel, and is heated until the lead
exhales. But if the ore is of poor or moderate quality, it must first be dried,
then crushed, and then to a centumpondium (of the lesser weights) an uncia
of lead is added, and it is heated in the scorifier until it melts. If it is not
soon melted by the fire, it should be sprinkled with a little powder of the
first order of fluxes, and if then it does not melt, more is added little by little
until it melts and exudes its slag; that this result may be reached sooner,
the powder which has been sprinkled over it should be stirred in with an iron
rod. When the scorifier has been taken out of the assay furnace, the alloy
should be poured into a hole in a baked brick; and when it has cooled and been
cleansed of the slag, it should be placed in a cupel and heated until it exhales
all its lead; the weight of silver which remains in the cupel indicates what
proportion of silver is contained in the ore.
We assay copper ore without lead, for if it is melted with it, the copper
usually exhales and is lost. Therefore, a certain weight of such an ore
is first roasted in a hot fire for about six or eight hours; next, when it has
cooled, it is crushed and washed; then the concentrates made by washing
are again roasted, crushed, washed, dried, and weighed. The portion which
it has lost whilst it is being roasted and washed is taken into account, and
these concentrates by washing represent the cake which will be melted out
of the copper ore. Place three centumpondia (lesser weights) of this, mixed
with three centumpondia (lesser weights) each of copper scales 30 , saltpetre,
and Venetian glass, mixed, into the triangular crucible, and place it in the iron
hoop which is set on the hearth in front of the double bellows. Cover the crucible
with charcoal in such a way that nothing may fall into the ore which is to be
melted, and so that it may melt more quickly. At first blow a gentle blast with
the bellows in order that the ore may be heated gradually in the fire; then
blow strongly till it melts, and the fire consumes that which has been added to
it, and the ore itself exudes whatever slag it possesses. Next, cool
the crucible which has been taken out, and when this is broken you will find
the copper; weigh this, in order to ascertain how great a portion of the ore
the fire has consumed. Some ore is only once roasted, crushed, and washed;
and of this kind of concentrates, three centumpondia (lesser weights) are
taken with one centumpondíum each of common salt, argol and glass−
galls. Heat them in the triangular crucible, and when the mixture has
cooled a button of pure copper will be found, if the ore is rich in this metal.
If, however, it is less rich, a stony lump results, with which the copper is
intermixed; this lump is again roasted, crushed, and, after adding stones
which easily melt and saltpetre, it is again melted in another crucible, and
there settles in the bottom of the crucible a button of pure copper. If you
wish to know what proportion of silver is in this copper button, melt it in a
cupel after adding lead. With regard to this test I will speak later.
Those who wish to know quickly what portion of silver the copper ore
contains, roast the ore, crush and wash it, then mix a little yellow litharge
with one centumpondium (lesser weights) of the concentrates, and put the
mixture into a scorifier, which they place under the muffle in a hot furnace for
the space of half an hour. When the slag exudes, by reason of the melting force
which is in the litharge, they take the scorifier out; when it has cooled, they
cleanse it of slag and again crush it, and with one centumpondíum of it they
mix one and a half uncíae of lead granules. They then put it into another
scorifier, which they place under the muffle in a hot furnace, adding to the
mixture a little of the powder of some one of the fluxes which cause ore to
melt; when it has melted they take it out, and after it has cooled, cleanse
it of slag; lastly, they heat it in the cupel till it has exhaled all of the lead,
and only silver remains.
Lead ore may be assayed by this method: crush half an uncía of
pure lead−stone and the same quantity of the chrysocolla which they call
borax, mix them together, place them in a crucible, and put a glowing coal
in the middle of it. As soon as the borax crackles and the lead−stone melts,
which soon occurs, remove the coal from the crucible, and the lead will settle
to the bottom of it; weigh it out, and take account of that portion of it
which the fire has consumed. If you also wish to know what portion of silver
is contained in the lead, melt the lead in the cupel until all of it exhales.
Another way is to roast the lead ore, of whatsoever quality it be, wash
it, and put into the crucible one centumpondium of the concentrates, together
with three centumpondia of the powdered compound which melts ore, mixed
together, and place it in the iron hoop that it may melt; when it has cooled,
cleanse it of its slag, and complete the test as I have already said. Another way is
to take two unciae of prepared ore, five drachmae of roasted copper, one uncia of
glass, or glass−galls reduced to powder, a semi−uncia of salt, and mix them. Put
the mixture into the triangular crucible, and heat it over a gentle fire to
prevent it from breaking; when the mixture has melted, blow the fire
vigorously with the bellows; then take the crucible off the live coals and
let it cool in the open air; do not pour water on it, lest the lead button being
acted upon by the excessive cold should become mixed with the slag, and the
assay in this way be erroneous. When the crucible has cooled, you will find
in the bottom of it the lead button. Another way is to take two unciae of
ore, a semi−uncia of litharge, two drachmae of Venetian glass and a semi−uncia
of saltpetre. If there is difficulty in melting the ore, add to it iron filings,
which, since they increase the heat, easily separate the waste from lead and
other metals. By the last way, lead ore properly prepared is placed in the
crucible, and there is added to it only the sand made from stones which easily
melt, or iron filings, and then the assay is completed as formerly.
You can assay tin ore by the following method. First roast it, then
crush, and afterward wash it; the concentrates are again roasted, crushed,
and washed. Mix one and a half centumpondia of this with one centum−
pondium of the chrysocolla which they call borax; from the mixture,
when it has been moistened with water, make a lump. Afterwards,
perforate a large round piece of charcoal, making this opening a palm deep,
three digits wide on the upper side and narrower on the lower side; when
the charcoal is put in its place the latter should be on the bottom and the
former uppermost. Let it be placed in a crucible, and let glowing coal be
put round it on all sides; when the perforated piece of coal begins to burn,
the lump is placed in the upper part of the opening, and it is covered with a
wide piece of glowing coal, and after many pieces of coal have been put round
it, a hot fire is blown up with the bellows, until all the tin has run out
of the lower opening of the charcoal into the crucible. Another way is to
take a large piece of charcoal, hollow it out, and smear it with lute, that the
ore may not leap out when white hot. Next, make a small hole through the
middle of it, then fill up the large opening with small charcoal, and put the
ore upon this; put fire in the small hole and blow the fire with the nozzle of
a hand bellows; place the piece of charcoal in a small crucible, smeared
with lute, in which, when the melting is finished, you will find a button
In assaying bismuth ore, place pieces of ore in the scorifier, and put
it under the muffle in a hot furnace; as soon as they are heated, they
drip with bismuth, which runs together into a button.
Quicksilver ore is usually tested by mixing one part of broken ore
with three−parts of charcoal dust and a handful of salt. Put the mixture into
a crucible or a pot or a jar, cover it with a lid, seal it with lute, place it on
glowing charcoal, and as soon as a burnt cinnabar colour shows in it, take
out the vessel; for if you continue the heat too long the mixture exhales the
quicksilver with the fumes. The quicksilver itself, when it has become cool, is
found in the bottom of the crucible or other vessel. Another way is to place
broken ore in a gourd−shaped earthen vessel, put it in the assay furnace,
and cover with an operculum which has a long spout; under the spout, put
an ampulla to receive the quicksilver which distills. Cold water should be
poured into the ampulla, so that the quicksilver which has been heated by the
fire may be continuously cooled and gathered together, for the quicksilver
is borne over by the force of the fire, and flows down through the spout of
the operculum into the ampulla. We also assay quicksilver ore in the very
same way in which we smelt it. This I will explain in its proper place.
Lastly, we assay iron ore in the forge of a blacksmith. Such ore is burned,
crushed, washed, and dried; a magnet is laid over the concentrates, and
the particles of iron are attracted to it; these are wiped off with a brush,
and are caught in a crucible, the magnet being continually passed over the
concentrates and the particles wiped off, so long as there remain any particles
which the magnet can attract to it. These particles are heated in the crucible
with saltpetre until they melt, and an iron button is melted out of them.
If the magnet easily and quickly attracts the particles to it, we infer that the
ore is rich in iron; if slowly, that it is poor; if it appears actually to repel
the ore, then it contains little or no iron. This is enough for the assaying of
I will now speak of the assaying of the metal alloys. This is done both
by coiners and merchants who buy and sell metal, and by miners, but most
of all by the owners and mine masters, and by the owners and masters of
the works in which the metals are smelted, or in which one metal is parted
First I will describe the way assays are usually made to ascertain what
portion of precious metal is contained in base metal. Gold and silver are
now reckoned as precious metals and all the others as base metals. Once
upon a time the base metals were burned up, in order that the precious metals
should be left pure; the Ancients even discovered by such burning what
portion of gold was contained in silver, and in this way all the silver was
consumed, which was no small loss. However, the famous mathematician,
Archimedes 31 , to gratify King Hiero, invented a method of testing the silver,
which was not very rapid, and was more accurate for testing a large mass
than a small one. This I will explain in my commentaries. The
alchemists have shown us a way of separating silver from gold by which
neither of them is lost 32 .
Gold which contains silver, 33 or silver which contains gold, is first rubbed
on the touchstone. Then a needle in which there is a similar amount of
gold or silver is rubbed on the same touchstone, and from the lines which are
produced in this way, is perceived what portion of silver there is in the gold,
or what portion of gold there is in the silver. Next there is added to the
silver which is in the gold, enough silver to make it three times as much as the
gold. Then lead is placed in a cupel and melted; a little later, a small
amount of copper is put in it, in fact, half an uncía of it, or half an uncia and
a sícílícus (of the smaller weights) if the gold or silver does not contain any
copper. The cupel, when the lead and copper are wanting, attracts the particles
of gold and silver, and absorbs them. Finally, one−third of a líbra of the gold,
and one libra 34 of the silver must be placed together in the same cupel and
melted; for if the gold and silver were first placed in the cupel and melted, as I
have already said, it absorbs particles of them, and the gold, when separated
from the silver, will not be found pure. These metals are heated until the
lead and the copper are consumed, and again, the same weight of each is melted
in the same manner in another cupel. The buttons are pounded with a
hammer and flattened out, and each little leaf is shaped in the form of a
tube, and each is put into a small glass ampulla. Over these there is poured
one uncia and one drachma (of the large weight) of the third quality aqua
valens, which I will describe in the Tenth Book. This is heated over a slow
fire, and small bubbles, resembling pearls in shape, will be seen to adhere
to the tubes. The redder the aqua appears, the better it is judged to be;
when the redness has vanished, small white bubbles are seen to be resting
on the tubes, resembling pearls not only in shape, but also in colour. After
a short time the aqua is poured off and other is poured on; when this has
again raised six or eight small white bubbles, it is poured off and the tubes are
taken out and washed four or five times with spring water; or if they are
heated with the same water, when it is boiling, they will shine more brilliantly.
Then they are placed in a saucer, which is held in the hand and gradually
dried by the gentle heat of the fire; afterward the saucer is placed over glowing
charcoal and covered with a charcoal, and a moderate blast is blown upon it
with the mouth and then a blue flame will be emitted. In the end the tubes
are weighed, and if their weights prove equal, he who has undertaken this work
has not laboured in vain. Lastly, both are placed in another balance−pan and
weighed; of each tube four grains must not be counted, on account of the
silver which remains in the gold and cannot be separated from it. From the
weight of the tubes we learn the weight both of the gold and of the silver
which is in the button. If some assayer has omitted to add so much silver to
the gold as to make it three times the quantity, but only double, or two and a
half times as much, he will require the stronger quality of aqua which
separates gold from silver, such as the fourth quality. Whether the aqua
which he employs for gold and silver is suitable for the purpose, or whether
it is more or less strong than is right, is recognised by its effect. That of
medium strength raises the little bubbles on the tubes and is found to colour
the ampulla and the operculum a strong red; the weaker one is found to
colour them a light red, and the stronger one to break the tubes. To pure
silver in which there is some portion of gold, nothing should be added when
they are being heated in the cupel prior to their being parted, except a bes
of lead and one−fourth or one−third its amount of copper of the lesser weights.
If the silver contains in itself a certain amount of copper, let it be weighed,
both after it has been melted with the lead, and after the gold has been parted
from it; by the former we learn how much copper is in it, by the latter how
much gold. Base metals are burnt up even to−day for the purpose of assay,
because to lose so little of the metal is small loss, but from a large mass of
base metal, the precious metal is always extracted, as I will explain in
Books X. and XI.
We assay an alloy of copper and silver in the following way. From a
few cakes of copper the assayer cuts out portions, small samples from small
cakes, medium samples from medium cakes, and large samples from large
cakes; the small ones are equal in size to half a hazel nut, the large
ones do not exceed the size of half a chestnut, and those of medium size come
between the two. He cuts out the samples from the middle of the
bottom of each cake. He places the samples in a new, clean, triangular
crucible and fixes to them pieces of paper upon which are written the weight
of the cakes of copper, of whatever size they may be; for example, he writes,
"These samples have been cut from copper which weighs twenty centum−
pondía." When he wishes to know how much silver one centumpondíum of
copper of this kind has in it, first of all he throws glowing coals into the
iron hoop, then adds charcoal to it. When the fire has become hot, the paper
is taken out of the crucible and put aside, he then sets that crucible on the
fire and gradually heats it for a quarter of an hour until it becomes red hot.
Then he stimulates the fire by blowing with a blast from the double bellows
for half an hour, because copper which is devoid of lead requires this time to
become hot and to melt; copper not devoid of lead melts quicker. When
he has blown the bellows for about the space of time stated, he removes the
glowing charcoal with the tongs, and stirs the copper with a splinter of wood,
which he grasps with the tongs. If it does not stir easily, it is a sign that the
copper is not wholly liquefied; if he finds this is the case, he again places a
large piece of charcoal in the crucible, and replaces the glowing charcoal which
had been removed, and again blows the bellows for a short time. When all
the copper has melted he stops using the bellows, for if he were to continue
to use them, the fire would consume part of the copper, and then that which
remained would be richer than the cake from which it had been cut; this is
no small mistake. Therefore, as soon as the copper has become sufficiently
liquified, he pours it out into a little iron mould, which may be large or small,
according as more or less copper is melted in the crucible for the purpose of the
assay. The mould has a handle, likewise made of iron, by which it is held
when the copper is poured in, after which, he plunges it into a tub of water
placed near at hand, that the copper may be cooled. Then he again dries the
copper by the fire, and cuts off its point with an iron wedge; the portion
nearest the point he hammers on an anvil and makes into a leaf, which he
cuts into pieces.
AIRON MOULD. BITS HANDLE.
Others stir the molten copper with a stick of linden tree charcoal, and
then pour it over a bundle of new clean birch twigs, beneath which is placed
a wooden tub of sufficient size and full of water, and in this manner the copper
is broken up into little granules as small as hemp seeds. Others employ straw
in place of twigs. Others place a broad stone in a tub and pour in enough
water to cover the stone, then they run out the molten copper from the
crucible on to the stone, from which the minute granules roll off; others
pour the molten copper into water and stir it until it is resolved into granules.
The fire does not easily melt the copper in the cupel unless it has been poured
and a thin leaf made of it, or unless it has been resolved into granules or
made into filings; and if it does not melt, all the labour has been undertaken
in vain. In order that they may be accurately weighed out, silver and lead
are resolved into granules in the same manner as copper. But to return
to the assay of copper. When the copper has been prepared by these
methods, if it is free of lead and iron, and rich in silver, to each centumpon−
díum (lesser weights) add one and a half unciae of lead (larger weights). If,
however, the copper contains some lead, add one uncia of lead; if it contains
iron, add two unciae. First put the lead into a cupel, and after it begins
to smoke, add the copper; the fire generally consumes the copper, together
with the lead, in about one hour and a quarter. When this is done, the silver
will be found in the bottom of the cupel. The fire consumes both of those
metals more quickly if they are heated in that furnace which draws in air. It
is better to cover the upper half of it with a lid, and not only to put on the
muffle door, but also to close the window of the muffle door with a piece of
charcoal, or with a piece of brick. If the copper be such that the silver can
only be separated from it with difficulty, then before it is tested with fire in
the cupel, lead should first be put into the scorifier, and then the copper should
be added with a moderate quantity of melted salt, both that the lead may
absorb the copper and that the copper may be cleansed of the dross which
abounds in it.
Tin which contains silver should not at the beginning of the assay be
placed in a cupel, lest the silver, as often happens, be consumed and converted
into fumes, together with the tin. As soon as the lead 35 has begun to fume
in the scorifier, then add that 36 to it. In this way the lead will take the
silver and the tin will boil and turn into ashes, which may be removed with a
wooden splinter. The same thing occurs if any alloy is melted in which there
is tin. When the lead has absorbed the silver which was in the tin, then,
and not till then, it is heated in the cupel. First place the lead with which
the silver is mixed, in an iron pan, and stand it on a hot furnace and let it
melt; afterward pour this lead into a small iron mould, and then beat it
out with a hammer on an anvil and make it into leaves in the same way as
the copper. Lastly, place it in the cupel, which assay can be carried out in
the space of half an hour. A great heat is harmful to it, for which reason
there is no necessity either to cover the half of the furnace with a lid or to
close up its mouth.
The minted metal alloys, which are known as money, are assayed in the
following way. The smaller silver coins which have been picked out from
the bottom and top and sides of a heap are first carefully cleansed; then, after
they have been melted in the triangular crucible, they are either resolved
into granules, or made into thin leaves. As for the large coins which weigh
a drachma, a sícílícus, half an uncía, or an uncia, beat them into leaves.
Then take a bes of the granules, or an equal weight of the leaves, and likewise
take another bes in the same way. Wrap each sample separately in paper,
and afterwards place two small pieces of lead in two cupels which have first
been heated. The more precious the money is, the smaller portion of lead
do we require for the assay, the more base, the larger is the portion required;
for if a bes of silver is said to contain only half an uncia or one uncia of copper,
we add to the bes of granules half an uncía of lead. If it is composed of equal
parts of silver and copper, we add an uncía of lead, but if in a bes of copper
there is only half an uncía or one uncía of silver, we add an uncía and a half
of lead. As soon as the lead has begun to fume, put into each cupel one of
the papers in which is wrapped the sample of silver alloyed with copper, and
close the mouth of the muffle with charcoal. Heat them with a gentle fire
until all the lead and copper are consumed, for a hot fire by its heat forces the
silver, combined with a certain portion of lead, into the cupel, in which way
the assay is rendered erroneous. Then take the beads out of the cupel and
clean them of dross. If neither depresses the pan of the balance in which it
is placed, but their weight is equal, the assay has been free from error; but
if one bead depresses its pan, then there is an error, for which reason the
assay must be repeated. If the bes of coin contains but seven unciae of
pure silver it is because the King, or Prince, or the State who coins the money,
has taken one uncia, which he keeps partly for profit and partly for the
expense of coining, he having added copper to the silver. Of all these
matters I have written extensively in my book De Precio Metallorum et
We assay gold coins in various ways. If there is copper mixed with
the gold, we melt them by fire in the same way as silver coins; if there is
silver mixed with the gold, they are separated by the strongest aqua valens;
if there is copper and silver mixed with the gold, then in the first place, after
the addition of lead, they are heated in the cupel until the fire consumes the
copper and the lead, and afterward the gold is parted from the silver.
It remains to speak of the touchstone 37 with which gold and silver are
tested, and which was also used by the Ancients. For although the assay made
by fire is more certain, still, since we often have no furnace, nor muffle, nor
crucibles, or some delay must be occasioned in using them, we can always
rub gold or silver on the touchstone, which we can have in readiness.
Further, when gold coins are assayed in the fire, of what use are they after−
ward? A touchstone must be selected which is thoroughly black and free
of sulphur, for the blacker it is and the more devoid of sulphur, the better it
generally is; I have written elsewhere of its nature 38 . First the gold is
rubbed on the touchstone, whether it contains silver or whether it is obtained
from the mines or from the smelting; silver also is rubbed in the same
way. Then one of the needles, that we judge by its colour to be of similar
composition, is rubbed on the touchstone; if this proves too pale, another
needle which has a stronger colour is rubbed on the touchstone; and if this
proves too deep in colour, a third which has a little paler colour is used. For
this will show us how great a proportion of silver or copper, or silver and
copper together, is in the gold, or else how great a proportion of copper is in
These needles are of four kinds. 39 The first kind are made of gold and
silver, the second of gold and copper, the third of gold, silver, and copper,
and the fourth of silver and copper. The first three kinds of needles are
used principally for testing gold, and the fourth for silver. Needles of this
kind are prepared in the following ways. The lesser weights correspond
proportionately to the larger weights, and both of them are used, not
only by mining people, but by coiners also. The needles are made in
accordance with the lesser weights, and each set corresponds to a bes,
which, in our own vocabulary, is called a mark. The bes, which is employed
by those who coin gold, is divided into twenty−four double sextulae, which
are now called after the Greek name ceratía; and each double sextula is
divided into four semi−sextulae, which are called granas; and each semí−sextula
is divided into three units of four siliquae each, of which each unit is called
a grenlín. If we made the needles to be each four síliquae, there would be
two hundred and eighty−eight in a bes, but if each were made to be a semí−sextula
or a double scripula, then there would be ninety−six in a bes. By these two
methods too many needles would be made, and the majority of them, by reason
of the small difference in the proportion of the gold, would indicate nothing,
therefore it is advisable to make them each of a double sextula; in this way
twenty−four needles are made, of which the first is made of twenty−three
duellae of silver and one of gold. Fannius is our authority that the Ancients
called the double sextula a duella. When a bar of silver is rubbed on the
touchstone and colours it just as this needle does, it contains one duella of gold.
In this manner we determine by the other needles what proportion of gold
there is, or when the gold exceeds the silver in weight, what proportion of
The needles are made 40 :
The 1st needle of 23 duellae of silver and 1 duella of gold.
The 2nd needle of 22 duellae of silver and 2 duellae of gold.
The 3rd needle of 21 duellae of silver and 3 duellae of gold.
The 4th needle of 20 duellae of silver and 4 duellae of gold.
The 5th needle of 19 duellae of silver and 5 duellae of gold.
The 6th needle of 18 duellae of silver and 6 duellae of gold.
The 7th needle of 17 duellae of silver and 7 duellae of gold.
The 8th needle of 16 duellae of silver and 8 duellae of gold.
The 9th needle of 15 duellae of silver and 9 duellae of gold.
The 10th needle of 14 duellae of silver and 10 duellae of gold.
The 11th needle of 13 duellae of silver and 11 duellae of gold.
The 12th needle of 12 duellae of silver and 12 duellae of gold.
The 13th needle of 11 duellae of silver and 13 duellae of gold.
The 14th needle of 10 duellae of silver and 14 duellae of gold.
The 15th needle of 9 duellae of silver and 15 duellae of gold.
The 16th needle of 8 duellae of silver and 16 duellae of gold.
The 17th needle of 7 duellae of silver and 17 duellae of gold.
The 18th needle of 6 duellae of silver and 18 duellae of gold.
The 19th needle of 5 duellae of silver and 19 duellae of gold.
The 20th needle of 4 duellae of silver and 20 duellae of gold.
The 21st needle of 3 duellae of silver and 21 duellae of gold.
The 22nd needle of 2 duellae of silver and 22 duellae of gold.
The 23rd needle of 1 duellae of silver and 23 duellae of gold.
The 24th needle of pure gold
By the first eleven needles, when they are rubbed on the touchstone, we
test what proportion of gold a bar of silver contains, and with the remaining
thirteen we test what proportion of silver is in a bar of gold; and also what
proportion of either may be in money.
Since some gold coins are composed of gold and copper, thirteen needles
of another kind are made as follows:
The 1st of 12 duellae of gold and 12 duellae of copper.
The 2nd of 13 duellae of gold and 11 duellae of copper.
The 3rd of 14 duellae of gold and 10 duellae of copper.
The 4th of 15 duellae of gold and 9 duellae of copper.
The 5th of 16 duellae of gold and 8 duellae of copper.
The 6th of 17 duellae of gold and 7 duellae of copper.
The 7th of 18 duellae of gold and 6 duellae of copper.
The 8th of 19 duellae of gold and 5 duellae of copper.
The 9th of 20 duellae of gold and 4 duellae of copper.
The 10th of 21 duellae of gold and 3 duellae of copper.
The 11th of 22 duellae of gold and 2 duellae of copper.
The 12th of 23 duellae of gold and 1 duellae of copper.
The 13th of pure gold.
These needles are not much used, because gold coins of that kind are
somewhat rare; the ones chiefly used are those in which there is much
copper. Needles of the third kind, which are composed of gold, silver, and
copper, are more largely used, because such gold coins are common. But since
with the gold there are mixed equal or unequal portions of silver and copper,
two sorts of needles are made. If the proportion of silver and copper is
equal, the needles are as follows:
Gold. Silver. Copper.
The 1st of 12 duellae 6 duellae 0 sextula 6 duellae 0 sextula
The 2nd of 13 duellae 5 duellae 1 sextula 5 duellae 1 sextula
The 3rd of 14 duellae 5 duellae 5 duellae
The 4th of 15 duellae 4 duellae 1 sextula 4 duellae 1 sextula
The 5th of 16 duellae 4 duellae 4 duellae
The 6th of 17 duellae 3 duellae 1 sextula 3 duellae 1 sextula
The 7th of 18 duellae 3 duellae 3 duellae
The 8th of 19 duellae 2 duellae 1 sextula 2 duellae 1 sextula
The 9th of 20 duellae 2 duellae 2 duellae
The 10th of 21 duellae 1 duellae 1 sextula 1 duellae 1 sextula
The 11th of 22 duellae 1 duellae 1 duellae
The 12th of 23 1 duellae
The 13th of pure gold.
Some make twenty−five needles, in order to be able to detect the two
scrípula of silver or copper which are in a bes of gold. Of these needles, the
first is composed of twelve duellae of gold and six of silver, and the same
number of copper. The second, of twelve duellae and one sextula of gold and
five duellae and one and a half sextulae of silver, and the same number of
duellae and one and a half sextulae of copper. The remaining needles are
made in the same proportion.
Pliny is our authority that the Romans could tell to within one scrípulum
how much gold was in any given alloy, and how much silver or copper.
Needles may be made in either of two ways, namely, in the ways of which
I have spoken, and in the ways of which I am now about to speak. If
unequal portions of silver and copper have been mixed with the gold, thirty−
seven needles are made in the following way:
Gold. Silver. Copper.
Duellae. Duellae Siliquae. Duellae Siliquae.
The 1st of 12 9 0 0 3 0 0
The 2nd of 12 8 0 0 4 0 0
The 3rd of 12 7 5
The 4th of 13 8 1/2 2 1/2
The 5th of 13 7 1/2 4 3 1 8
The 6th of 13 6 1/2 8 4 1 4
The 7th of 14 7 1 2 1
The 8th of 14 6 1 8 3 1/2 4
The 9th of 14 5 1 1/2 4 4 8
The 10th of 15 6 1 1/2 2 1/2
The 11th of 15 6 3
The 12th of 15 5 1/2 3 1 1/2
The 13th of 16 6 2
The 14th of 16 5 1/2 4 2 1 8
The 15th of 16 4 1 8 3 1/2 4
The 16th of 17 5 1/2 0 1 1 1/2
The 17th of 17 4 1 8 2 1/2 4
The 18th of 17 4 4 2 1 1/2 8
The 19th of 18 4 1 1 1
The 20th of 18 4 0 2 1
The 21st of 18 3 1 2
The 22nd of 19 2 1 1/2 1 1/2
The 23rd of 19 3 1/2 4 1 1 8
The 24th of 19 2 1 1/2 8 2 4
The 25th of 20 3 1
The 26th of 20 2 1 8 1 1/2 4
The 27th of 20 2 1/2 4 1 1 8
The 28th of 21 2 1/2 1 1/2
The 29th of 21 2 1
The 30th of 21 1 1 1/2 1 1/2
The 31st of 22 1 1 1
The 32nd of 22 1 1/2 4 0 1 8
The 33rd of 22 1 8 1 1/2 4
The 34th of 23 1 1/2 1/2
The 35th of 23 1 8 1/2 4
The 36th of 23 1 4 1/2 8
The 37th of pure gold.
Since it is rarely found that gold, which has been coined, does not amount to
at least fifteen duellae of gold in a bes, some make only twenty−eight needles, and
some make them different from those already described, inasmuch as the
alloy of gold with silver and copper is sometimes differently proportioned.
These needles are made:
Gold. Silver. Copper.
Duellae. Duellae Siliquae. Duellae Siliquae.
The 1st of 15 6 1 8 2 1/2 4
The 2nd of 15 6 4 2 1 1/2 8
The 3rd of 15 5 1/2 3 1 1/2
The 4th of 16 6 1/2 1 1 1/2
The 5th of 16 5 1 8 2 1/2 4
The 6th of 16 4 1 1/2 8 3 4
The 7th of 17 5 1 4 1 1/2 8
The 8th of 17 5 4 1 1 1/2 8
The 9th of 17 4 1 4 2 1/2 8
The 10th of 18 4 1 1 1
The 11th of 18 4 2
The 12th of 18 3 1 2 1
The 13th of 19 3 1 1/2 4 1 8
The 14th of 19 3 1/2 4 1 1 8
The 15th of 19 2 1 1/2 4 2 8
The 16th of 20 3 1
The 17th of 20 2 1 1
The 18tth of 20 2 2
The 19th of 21 2 1/2 4 1 8
The 20th of 21 1 1 1/2 4 1 8
The 21st of 21 1 1 8 1 1/2 4
The 22nd of 22 1 1 8 1/2 4
The 23rd of 22 1 1 1
The 24th of 22 1 1/2 4 1 8
The 25th of 23 1 1/2 4 8
The 26th of 23 1 1/2 1/2
The 27th of 23 1 8 1/2 4
The 28th of pure gold
Next follows the fourth kind of needles, by which we test silver coins
which contain copper, or copper coins which contain silver. The bes by
which we weigh the silver is divided in two different ways. It is either
divided twelve times, into units of five drachmae and one scrípulum each,
which the ordinary people call nummi 41 ; each of these units we again divide
into twenty−four units of four siliquae each, which the same ordinary people
call a grenlin; or else the bes is divided into sixteen semunciae which
are called loths, each of which is again divided into eighteen units of four
silíquae each, which they call grenlín. Or else the bes is divided into
sixteen semuncíae, of which each is divided into four drachmae, and
each drachma into four pfennige. Needles are made in accordance with
each method of dividing the bes. According to the first method, to the
number of twenty−four half nummí; according to the second method, to the
number of thirty−one half semuncíae, that is to say a sícílícus; for if the
needles were made to the number of the smaller weights, the number of
needles would again be too large, and not a few of them, by reason of the
small difference in proportion of silver or copper, would have no significance.
We test both bars and coined money composed of silver and copper by both
scales. The one is as follows: the first needle is made of twenty−three
parts of copper and one part silver; whereby, whatsoever bar or coin, when
rubbed on the touchstone, colours it just as this needle does, in that bar or
money there is one twenty−fourth part of silver, and so also, in accordance
with the proportion of silver, is known the remaining proportion of the copper.
The 1st needle is made of 23 parts of copper and 1 of silver.
The 2nd needle is made of 22 parts of copper and 2 of silver.
The 3rd needle is made of 21 parts of copper and 3 of silver.
The 4th needle is made of 20 parts of copper and 4 of silver.
The 5th needle is made of 19 parts of copper and 5 of silver.
The 6th needle is made of 18 parts of copper and 6 of silver.
The 7th needle is made of 17 parts of copper and 7 of silver.
The 8th needle is made of 16 parts of copper and 8 of silver.
The 9th needle is made of 15 parts of copper and 9 of silver.
The 10th needle is made of 14 parts of copper and 10 of silver.
The 11th needle is made of 13 parts of copper and 11 of silver.
The 12th needle is made of 12 parts of copper and 12 of silver.
The 13th needle is made of 11 parts of copper and 13 of silver.
The 14th needle is made of 10 parts of copper and 14 of silver.
The 15th needle is made of 9 parts of copper and 15 of silver.
The 16th needle is made of 8 parts of copper and 16 of silver.
The 17th needle is made of 7 parts of copper and 17 of silver.
The 18th needle is made of 6 parts of copper and 18 of silver.
The 19th needle is made of 5 parts of copper and 19 of silver.
The 20th needle is made of 4 parts of copper and 20 of silver.
The 21st needle is made of 3 parts of copper and 21 of silver.
The 22nd needle is made of 2 parts of copper and 22 of silver.
The 23rd needle is made of 1 parts of copper and 23 of silver.
The 24th of pure silver.
The other method of making needles is as follows:
Semunciae Sícilící Semuncíae Sícilící
The 1st is of 15 1
The 2nd is of 14 1 1 1
The 3rd is of 14 2
The 4th is of 13 1 2 1
The 5th is of 13 3
The 6th is of 12 1 3 1
The 7th is of 12 4
The 8th is of 11 1 1
The 9th is of 11 5
The 10th is of 10 1 5 1
The 11th is of 10 6
The 12th is of 9 1 6 1
The 13th is of 9 7
The 14th is of 8 1 7 1
The 15th is of 8 8
The 16th is of 7 1 8 1
The 17th is of 7 9
The 18th is of 6 1 9 1
The 19th is of 6 10
The 20th is of 5 1 10 1
The 21st is of 5 11
The 22nd is of 4 1 11 1
The 23rd is of 4 12
The 24th is of 3 1 12 1
The 25th is of 3 13
The 26th is of 2 1 13 1
The 27th is of 2 14
The 28th is of 1 1 14 1
The 29th is of 1 15
The 30th is of 1 15 1
The 31st of pure silver.
So much for this. Perhaps I have used more words than those most
highly skilled in the art may require, but it is necessary for the understanding
of these matters.
I will now speak of the weights, of which I have frequently made mention.
Among mining people these are of two kinds, that is, the greater weights and
the lesser weights. The centumpondium is the first and largest weight, and of
course consists of one hundred librae, and for that reason is called a
The various weights are:
1st = 100 librae = centumpondium.
2nd = 50 librae
3rd = 52 librae
4th = 16 librae
5th = 8 librae
6th = 4 librae
7th = 2 librae
8th = 1 libra.
This libra consists of sixteen unciae, and the half part of the libra is
the selibra, which our people call a mark, and consists of eight unciae, or, as
they divide it, of sixteen semunciae :
9th = 8 unciae.
10th = 8 semunciae.
11th = 4 semunciae.
12th = 2 semunciae.
13th = 1 semuncia.
14th = 1 sicilicus.
15th = 1 drachma.
16th = 1 dimidi−drachma.
The above is how the "greater" weights are divided. The "lesser"
weights are made of silver or brass or copper. Of these, the first and largest
generally weighs one drachma, for it is necessary for us to weigh, not only
ore, but also metals to be assayed, and smaller quantities of lead. The first
of these weights is called a centumpondium and the number of librae in it
corresponds to the larger scale, being likewise one hundred 42 .
The 1st is called 1 centumpondium.
The 2nd is called 50 librae.
The 3rd is called 25 librae.
The 4th is called 16 librae.
The 5th is called 8 librae.
The 6th is called 4 librae.
The 7th is called 2 librae.
The 8th is called 1 librae.
The 9th is called 1 selibra.
The 10th is called 8 semunciae.
The 11th is called 4 semunciae.
The 12th is called 2 semunciae.
The 13th is called 1 semunciae.
The 14th is called 1 sicilicus.
The fourteenth is the last, for the proportionate weights which correspond
with a drachma and half a drachma are not used. On all these weights of
the lesser scale, are written the numbers of librae and of semunciae. Some
copper assayers divide both the lesser and greater scale weights into divisions
of a different scale. Their largest weight of the greater scale weighs one
hundred and twelve líbrae, which is the first unit of measurement.
1st = 112 librae.
2nd = 64 librae.
3rd = 32 librae.
4th = 16 librae.
5th = 8 librae.
6th = 4 librae.
7th = 2 librae.
8th = 1 librae.
9th = 1 selibra or sixteen semunciae.
10th = 8 semunciae.
11th = 4 semunciae.
12th = 2 semunciae.
13th = 1 semunciae.
As for the selíbra of the lesser weights, which our people, as I have often
said, call a mark, and the Romans call a bes, coiners who coin gold, divide it
just like the greater weights scale, into twenty−four units of two sextulae
each, and each unit of two sextulae is divided into four semí−sextulae and
each semí−sextula into three units of four síliquae each. Some also divide
the separate units of four siliquae into four individual síliquae, but most,
omitting the semi−sextulae, then divide the double sextula into twelve units of
four sílíquae each, and do not divide these into four individual siliquae. Thus
the first and greatest unit of measurement, which is the bes, weighs twenty−
four double sextulae.
The 2nd = 12 double sextulae.
The 3rd = 6 double sextulae.
The 4th = 3 double sextulae.
The 5th = 2 double sextulae.
The 6th = 1 double sextulae.
The 7th = 2 semí−sextulae or four semí−sextulae.
The 8th = 1 semi−sextula or 3 units of 4 síliquae each.
The 9th = 2 units of four siliquae each.
The 10th = 1 units of four siliquae each.
Coiners who mint silver also divide the bes of the lesser weights in the same
way as the greater weights; our people, indeed, divide it into sixteen sem−
uncíae, and the semuncia into eighteen units of four silíquae each.
There are ten weights which are placed in the other pan of the balance,
when they weigh the silver which remains from the copper that has been
consumed, when they assay the alloy with fire.
The 1st = 16 semunciae = 1 bes.
The 2nd = 8 semunciae
The 3rd = 4 semunciae
The 4th = 2 semunciae
The 5th = 1 semunciae or 18 units of 4 sílíquae each.
The 6th = 9 units of 4 siliquae each.
The 7th = 6 units of 4 siliquae each.
The 8th = 3 units of 4 siliquae each.
The 9th = 2 units of 4 siliquae each.
The 10th = 1 units of 4 siliquae each.
The coiners of Nuremberg who mint silver, divide the bes into sixteen sem−
uncíae, but divide the semuncía into four drachmae, and the drachma into
four pfenníge. They employ nine weights.
The 1st = 16 semuncíae.
The 2nd = 8 semuncíae.
The 3rd = 4 semuncíae.
The 4th = 2 semuncíae.
The 5th = 1 semuncíae.
For they divide the bes in the same way as our own people, but since they
divide the semuncía into four drachmae,
the 6th weight = 2 drachmae.
the 7th weight = 1 drachma or 4 pfenníge.
the 8th weight = 2 pfenníge.
the 9th weight = 1 pfenníg
The men of Cologne and Antwerp 43 divide the bes into twelve units of
five drachmae and one scrípulum, which weights they call nummi. Each
of these they again divide into twenty−four units of four siliquae each,
which they call grenlíns. They have ten weights, of which
the 1st = 12 nummi = 1 bes.
the 2nd = 6 nummi
the 3rd = 3 nummi
the 4th = 2 nummi
the 5th = 1 nummi = 24 units of 4 siliquae each.
the 6th = 12 units of 4 siliquae each.
the 7th = 6 units of 4 siliquae each.
the 8th = 3 units of 4 siliquae each.
the 9th = 2 units of 4 siliquae each.
the 10th = 1 units of 4 siliquae each.
And so with them, just as with our own people, the mark is divided into
two hundred and eighty−eight grenlíns, and by the people of Nuremberg it is
divided into two hundred and fifty−six pfennige. Lastly, the Venetians divide
the bes into eight unciae. The uncia into four sicilici, the sicilicus into
thirty−six siliquae. They make twelve weights, which they use whenever they
wish to assay alloys of silver and copper. Of these
the 1st = 8 unciae = 1 bes.
the 2nd = 4 uncíae
the 3rd = 2 uncíae
the 4th = 1 uncíae or 4 sícílicí.
the 5th = 2 sícilíc´.
the 6th = 1 sícilicus.
the 7th = 18 siliquae.
the 8th = 9 siliquae.
the 9th = 6 siliquae.
the 10th = 3 siliquae.
the 11th = 2 siliquae.
the 12th = 1 siliquae.
Since the Venetians divide the bes into eleven hundred and fifty−two siliquae,
or two hundred and eighty−eight units of 4 siliquae each, into which number
our people also divide the bes, they thus make the same number of siliquae,
and both agree, even though the Venetians divide the bes into smaller
This, then, is the system of weights, both of the greater and the lesser kinds,
which metallurgists employ, and likewise the system of the lesser weights
which coiners and merchants employ, when they are assaying metals and
coined money. The bes of the larger weight with which they provide them−
selves when they weigh large masses of these things, I have explained in my
work De Mensuris et Ponderibus, and in another book, De Precio Metallorum
There are three small balances by which we weigh ore, metals, and
fluxes. The first, by which we weigh lead and fluxes, is the largest among these
smaller balances, and when eight unciae (of the greater weights) are placed in
one of its pans, and the same number in the other, it sustains no damage.
The second is more delicate, and by this we weigh the ore or the metal, which
is to be assayed; this is well able to carry one centumpondium of the lesser
weights in one pan, and in the other, ore or metal as heavy as that weight.
The third is the most delicate, and by this we weigh the beads of gold or
silver, which, when the assay is completed, settle in the bottom of the cupel.
But if anyone weighs lead in the second balance, or an ore in the third, he
will do them much injury.
Whatsoever small amount of metal is obtained from a centumpondium
of the lesser weights of ore or metal alloy, the same greater weight of metal
is smelted from a centumpondium of the greater weight of ore or metal alloy.
AFIRST SMALL BALANCE. BSECOND. CTHIRD, PLACED IN A CASE.
END OF BOOK VII.