The transparent yellow chrysoberyl when cut as a " brilliant" might bo mistaken for a yellow diamond, although the test of hardness would easily distinguish the latter gem. The difference between the chrysoberyl and the yellow topaz is easily determined, as the topaz becomes electric when heated, while the chrysoberyl does not develop pyro-electricity. The basal cleavage of the topaz will also assist in the determination, if present.
The chrysoberyl is cut on a copper wheel with emery, and polished with Tripoli powder.
The chrysoberyl is found as rolled pebbles in the alluvial deposits in Cevlon, Brazil, and Moravia. It is found embedded in mica slate in the Ural Mountains ; it has been found in granite in the United States of America, and has also been found in Ireland.
It is doubtful whether this gem has yet been discovered in New South "Wales; it has been stated, however, that a fragment was found in the Macquarie Eiver. There is no reason why this gem should not exist in the Colony.
CHRYSOLITE.
Crystalline system—Rhombic.
Hardness—6—7.
Specific gravity—3"3—3'5.
Lustre—Vitreous.
Cleavage—Parallel to the brachypinakoid.
Composition—Silicate of Magnesia and Protoxide of Iron (MgO,FeO)3 SiO2. The ratio of iron to magnesia is not constant.
This gem is often mistaken for the chrysoberyl, but differs widely from it in composition and other characteristics, as fully stated under that stone.
The chrysolite is the "golden stone" of the ancients, and was at one time considered of very great value, more so even than the diamond.
In the eleventh century we find Marbodus, Bishop of Bennes, in a poem called " Lapidarium," writing of it as follows :—
" The golden Chrysolite a fiery blaze
Mixed with the hues of ocean's green displays."
This proves that the term " golden " was applied to this stone through many centuries.
It was in ancient times much used for ornamental purposes, especially by the ladies ; but it has become of far less importance during late years, although the demand for it revived some years ago, and it was then much used; but at the present time its value is but small, fine specimens being bought for a few shillings per carat.
The chrysolite is known as peridot when of -a deep olive-green colour, and olivine when yellowish-green. The finest specimens of chrysolite resemble the emerald in colour, and the colour fixes the value of the stone ; the darker the green the higher the price.
Unfortunately the hardness is low, and the stone is readily scratched and dulled by wear, a circumstance perhaps of sufficient importance to account for its depreciation as an ornamental gem-stone.
The chrysolite is electric by friction, but does not develop pyro-electricity, a circumstance sufficiently distinct to determine it from green tourmaline, which it somewhat resembles.
Flickr
Stumbleupon
Scribd