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A Variety Of Beryl Stone And The Most Costly of Gems,The Emerald

Considering the particular emerald which is a variety of Beryl—although the name emerald in the trade is applied somewhat loosely to any stone which is of the same colour, or approaching the colour of the beryl variety—this emerald only differs chemically from the beryl, just described, in possessing an addition of oxide of chromium


In shape, crystallisation, fracture and hardness, it is the same, and often contains, in addition to the chromium, the further addition of traces of carbonate of lime, magnesia, and occasionally faint traces of hornblende and mica, which evidently result from its intimate association with the granite rock and gneiss, amongst which it is mostly found, the latter rocks being of a slaty nature, in layers or plates, and, like granite, containing mica, pyrites, felspar, quartz, etc.


Emeralds have been known from very early times, and are supposed to have been found first in the mines of ancient Egypt. They were considered amongst the rarest and the most costly of gems, and it was the custom, when conferring lavish honour, to engrave or model emeralds for presentation purposes.


Thus we find Pliny describes Ptolemy giving Lucullus, on his landing at Alexandria, an emerald on which was engraved his portrait. Pliny also relates how the short-sighted Nero watched the fights of gladiators through an eye-glass made of an emerald, and in ancient times, in Rome, Greece, and Egypt, eye-glasses made of emeralds were much valued.

Many of these, as well as engraved and carved emeralds, have been discovered in ruins and tombs of those periods.

The copper emerald is rare; it is a hydrous form of copper silicate, CuOSiO2 + H2O, of a beautiful emerald green, varying from transparent to translucent.
It exhibits double refraction, and is a crystallised mineral, brittle, and showing a green streak.
This is less hard than the real emerald, is heavier, deeper in colour, and is usually found in crystals, in cavities of a particular kind of limestone which exists at Altyn-Tübe, a hill in the Altai Mountains, in the Urals, and in North and Central America.

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