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ALABASTER
(CALCITE, GYPSUM)
The term alabaster is derived from a kind of ointment vases called alabastra, which the Egyptians and peoples of a later period were accus­tomed to carve out of stone. This stone was largely a stalagmitic calcite obtained at Thebes, but it is probable that gypsum was also used to some extent. At the present time the term is used loosely for either of these minerals when employed for the manufacture of ornamental objects, although stalagmitic calcite is now more generally designated as onyx.
Both calcite and gypsum are soft minerals, the hardness of the former being 3, and that of the latter 2. They are not therefore fitted to endure wear, and can only be employed for objects such as vases, boxes, statuary, etc., not likely to be subjected to much attrition. Both stalagmitic calcite, however, and gypsum take an excellent polish, and preserve it if properly cared for.
The term alabaster when referred to gypsum is limited to the fine­grained granular variety usually white or delicately shaded. It is obtained largely at Castelino, near Leghorn, in Italy, and is used for carvings of various sorts. Objects are often sold under the names of alabaster that have been made out of plaster of paris by molding. These can be distinguished from true alabaster by their lack of translucency.
Another form of gypsum used for ornamental purposes is that known as satin spar. This is white, with a delicately fibrous structure, and exhibits when polished a beautiful silky luster and pearly opalescence. Large quantities of this cut in the form of necklaces, charms, etc., are often sold at Niagara Falls and vicinity to tourists as made from material found at the Falls. Although gypsum occurs there, it is not in this form, and the material used in this way is really obtained in Wales.
Objects made from calcite can usually be detected by their softness, as they scratch easily and deeply with a knife, and by their effervescing when touched with a drop of any common acid. In the form of Mexican onyx calcite is extensively used for ornamental purposes, and many locally fashioned stones, such as the Petoskey, Michigan, fossil corals (often called agates), and the Gibraltar stone, of Gibraltar, belong to this mineral species.
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