LAPIS LAZULI. · 323
Greeks and Romans are said to have called it by the name of sapphire, denominating that with specks of iron pyrites the sapphirus regilus ; Pliny called it the cyanus. It was formerly used as a strengthening medicine.
Lapis
lazuli very seldom occurs crystallized ; its regular form is the
oblique four-sided prism ; it mostly occurs compact, and in grains and
specks, with an uneven and conchoidal fracture; it is translucent on
the edges; its lustre is nearly vitreous and shining ; structure
foliated ; its color is fine azure-blue, with different shades, often
interspersed with spots and veins of pyrites. It scratches glass, but
is attacked by quartz and by the file ; its specific gravity is 2-3
; before the blowpipe and on charcoal it with difficulty runs into a
white glass, but with borax it fuses with effervescence into a limpid
glass. It consists of lime, magnesia, alumina, and silex, with soda,
protoxide of iron, and sulphuric acid.
It is generally called in trade, the Armenian-stone.
It
is found in gangues of the older formations, and in Bucharia; it exists
in granite rocks, and is disseminated in all veins of thin capacity ;
on the Baikal Lake it is found in solid pieces ; also, in Siberia,
Thibet, China, Chili, and Great Bucharia.
Lapis
lazuli is much used for jewelry, such as rings, pins, crosses,
ear-rings, &c. The best pieces are generally cut out from larger
lumps by means of copper saws and emery, then ground with emery on a
lead wheel, and polished with rotten-stone on a tin wheel. The rocks
which yield lapis lazuli, where it is contained in specks, are likewise
cut for ornamental purposes, such as snuffboxes, vases, candlesticksr cups, columns, cane-heads, &c. ; also,
for architectural ornaments and stone mosaic; the larger specimens,
having specks regularly disseminated on a white ground of the rock, are
those selected for cutting.
