Who knew it was also a unit of measure? The only citation for sense 3 of the noun form is... another dictionary. Also, I own a (much more recent) copy of this dictionary. Old dictionaries tend to be veritable fonts of old and interesting, though not always useful, information. One of my favorite things.
alabaster, n. and adj.
1. An ornamental stone consisting of a fine-grained, compact, translucent form of gypsum or (esp. with reference to ancient artefacts) calcite, typically white or tinted or clouded with yellow, red, and other colours, and suitable for carving into vases, figures, etc.
In modern use the term alabaster generally refers to a form of gypsum, but ancient alabaster statuary is often calcitic.
burnt, oriental alabaster: see the first element.
2. Ancient History. A vessel for holding perfume, unguents, or ointments; = ALABASTRUM n. 1, ALABASTRON n.
3. A unit of capacity for liquids equal to half a sextary (approx. 0.6 pint, 0.3 litre). Obsolete. rare.
1. Made out of alabaster.
2. fig. Esp. of skin: like alabaster in whiteness or smoothness.