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EMERALD.
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205
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It
is not corroded by acids, but is soluble in salts of phosphorus. It is
found in micaceous schists at Salzburg, in the mountains of Sahara, in
the argillaceous earths of Peru and of Siberia, at Henbachthal, in
Germany, at the height of 3,700 feet above the level of the sea.
The Western emerald is now procured principally from America, -where the mines of Muzo, in New Granada, are celebrated.
Emeralds of very good quality are dug up at Odont-chelong, in Siberia, and at Ava, in India.
This gem has often imperfections and flaws inside which quite deprive it of its lustre ; there are some, too, very opaque.
It
has been thought that the green colour of the emerald is dtrived from
oxide of chrome ; but Levy, in the analysis, perceiving such a small
quantity of chromic acid, formed the opinion that it was produced by
some organic substance, which he imagined was a carburet of hydrogen
similar to the chlorophyll which colours the leaves of plants.
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