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PRECIOUS STONES.
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obtained.
Unlike the Siamese Sapphires, their images in the dichroscope are blue
and straw-colour. They tend to be too dark in colour in many cases.
In
Ceylon they occur in the gem gravels around Adam's Peak with the
associates mentioned under Euby. Most of the Sapphires are found in the
southern parts of the island; they are supposed to have been developed
in the crystalline limestones of the district, but as yet have not been
found in situ. The stones are, like the accompanying Rubies, very brilliant, but rather light in colour.
A
more interesting deposit, and one which is, in addition, of commercial
importance, is that near the village of Soomjam in Kashmir. Here in the
early 'eighties a landslip exposed a mass of garnetiferous gneiss with
interfolia-tions of an altered limestone containing granitic veins, and
in this rock the Sapphires have been found in situ associated
with Tourmaline. Most of the gems, however, are found in detrital
matter derived from the weathering of the neighbouring rocks.
Specimens of very large size have been obtained—up to 300 carats ; many
are too pale.
In
the United States there are two areas of importance as producers of
Sapphires. One is the Culsagee mine in Macon County, North Carolina,
where the mineral occurs with Spinel, Tremolite, Tourmaline, Magnetite,
Eutile, Chromite, Olivine, and Mica, in gneiss. The other district is
in Montana. Near Helena is a glacial moraine known as the El Dorado Bar
and in this Sapphire has been found with Topaz, Garnet, Cassiterite,
Quartz and Cyanite. In addition it has been found in situ in Montana in a dyke with Pyrope, at Yogo Creek near Judith River, of a fine cornflower blue.
p.s.
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