Information from the Getty AAT
alabaster (mineral)
Fine-grained marblelike variety of gypsum that is easy to carve but is rather fragile; it has been used as a sculpture material, ornamental building work, vases, small decorative carvings, and powdered for use as a paper filler and paint pigment called mineral white or terra alba. Alabaster is usually a translucent white or pink but may also be a muted red, yellow or gray. It is soft and can be scratched slightly with a fingernail. It also dissolves slowly in wet environments.