ALABASTER, a name applied to two different mineral sub stances. The alabaster of the ancients is mostly a granular aggregate of crystals of calcium carbonate—i.e., it is really a marble (q.v.). The alabaster of modern times is a granular form of the mineral gypsum (q.v.). It is usually white, pink or yellow ish in colour, often with darker streaks and patches, and is very soft (hardness 1.5 to 2) so that it can be scratched by the finger nail. It can be readily distinguished from marble by the fact that it does not effervesce with acid. Alabaster is found in beds interstratified with red sandstones and marls deposited in the beds of salt lakes during an arid period: in England, chiefly in the Keuper marls of the midlands, especially at Chellaston in Derbyshire, Fauld in Staffordshire, and near Newark, Notting hamshire, also in the neighbourhood of Carlisle, near Watchet in Somerset and Penarth in Glamorgan, all in the Trias.
On the Continent the centre of the alabaster trade is Florence, where it is found in Miocene and Pliocene strata, and is ex tensively used for statuary work and carving of ornamental ob jects. The best kind is pure white and translucent, but by careful heating in nearly boiling water it can be made nearly opaque, resembling marble. This appears to be due to partial dehydration.
(R. H. RA.)