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178 PRECIOUS STONES
parent
stones cut like poor garnets. Composition: silica, 29.3; alumina, 53.5;
peroxide of iron, 17.2. It darkens but does not fuse before the
blow-pipe. It is found in Europe and the Eastern States. Staurolites
are used abroad as charms, and there is a legend in Brittany, France,
that those found there were cast from heaven.
Sunstone,
or aventurine feldspar, is like moonstone, a variety of orthoclase, and
is very similar, except that it is reddish gray or reddish gold to
gray, and shows internal prismatic reflections arising from minute
crystals of oxide of iron or mica scattered throughout the stone. It is
found in various parts of Europe, Ceylon, and the United States, but is
seldom used, as an imitation called " goldstone" has been preferred.
Thomsonite
was named after Dr. Thomas Thomson, of Glasgow. Crystallization
trimetric, in right rectangular prisms; usually in masses, and found as
rolled pebbles in size from a pin-head to an inch in diameter.
Hardness, 5 to 6, brittle; specific gravity, 2.3 to 2.4. Lustre
vitreous to pearly; translucent. Composition: silica, 37.4; alumina,
31.8; lime, 13; soda, 4.8; water, 13. Edges round merely at a great
heat. The pebbles found on the beach at Lake Superior show a series of
concentric layers of color in shades of flesh-red, creamy white,
yellow, and green, similar when polished to an eye-agate. They are cut
by simply rounding off and polishing to show the markings.
Thulite
is a red variety of epidote, containing fourteen per cent, of oxide of
manganese. It is pink in color, whereas the manganesian epidote is of
the darker shades of red. Lustre vitreous; translucent to opaque.
Thulite is being cut for brooches and as drops for pendants. It
appears, when cut, an opaque, mottled pink stone. It fuses to a black
glass.
Vesuvianite, known also as idocrase and xanthite, is named after Vesuvius, in the lava of which it was first found,
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