Ch. 9: Synthetic Gems

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Hannay's experiments have been successful, and bis pro­duct proved to be minute diamonds. See a recent paper in the Mineralogical Magazine. (Hannay's Artificial Diamonds: F. A. Bannister and K. Lonsdale, Min. Mag., Vol. XXVI, No. 181, June 1943, pp. 315-324.) Hannay's minute diamonds were the result of success in his experiments.
ARTIFICIAL RUBY. In 1837, Gaudin made artificial rubies by fusing alum at a high temperature with a little chromium as a pigment. In 1847, Edelman made white sapphire by fusing alumina in boric acid. Frenic and Freil made, in 1877, crystal corundum from which small stones could be cut. Frimy and Verneuil manufactured artificial ruby by fusing BaF2 and Al2O3 with a little chromium at red heat. There were also others working on the same fines.
THE VERNEUIL PROCESS. In 1902 Verneuil an­nounced to the world that he could manufacture ruby on a commercial scale. Other varieties of corundum and spinel also could be manufactured. The manufactured stones are known as synthetic gems, e.g. synthetic rubies, synthetic sapphire, synthetic spinel. They are akin to the natural stones chemically and physically except for certain features.
The apparatus consists of an inverted oxyhydrogen blowpipe. Purified and finely powdered alumina is kept in receptacles, the bottom being in a fine sieve. The receptacle is tapped by a mechanism, when a small amount of the powder falls into a flame and collects in a support. The fused alumina takes a carrot shape, and is known as a boule or birne, the broader part being uppermost. When the boule reaches 300-400 carats the furnace is closed, allowed to cool for an hour and the boule is removed with suitable tongs. Boules may go even up to 750 carats. If no colouring agent is added, a white sapphire is produced.
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Ch. 9: Synthetic Gems Page of 187 Ch. 9: Synthetic Gems
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