The yellow variety, called by the Italians, alabastro ago· tato, is
found at Sienna; another variety of a bluish color, obtained at
Guercieto, is remarkably beautiful, being marked with variegated shades
of purple, blue, and red. The above alabasters are carbonates of lime.
The
principal manufactory of alabaster ornaments is at Valterra, thirty-six
miles from Leghorn, where about five thousand persons live by this kind
of labor. In making, they require great care, and must be preserved
from dust, as the alabaster is difficult to clean. Talcum, commonly
called French chalk, will remove dirt, but the best mode of restoring
the color, is to bleach the alabaster on a grass-plat. Gum water is the
only cement for uniting broken parts.
Plaster of Paris is
likewise a compact gypsum, but contains a small portion of carbonic
acid, which makes it effervesce when treated with acids. It was
formerly exported only from Montmartre, near Paris, hence its name ;
it is much used in ornamenting rooms in stucco, in taking impressions
of medals, in casting statues, busts, vases, time-piece stands,
candelabras, obelisks, and for many other purposes.
The
common plaster of Paris is ground after being calcined ; and in this
condition it has the property of forming a pliable mass with water,
which soon hardens, and assumes the consistency of stone.
Oriental
alabaster is not a sulphate but a true carbonate of lime, and on
account of its peculiar tint and transparency, and as it appears that
it was formed similar to stalagmite, it was called by the ancients,
alabaster ; the large vase of this Oriental alabaster which was so
justly and so much admired by the thousands of spectators at the London
Exhibition, was executed by Dallamada, of Rome. It was really a
magnificent piece of workmanship, being
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