The
synthetic stones were originally made by fusing together fragments of
the natural material, and the stones were known as reconstructed gems,
e.g. ruby. The stones were not good, being poor in colour and brittle.
Some good stones were made and sold, but this process has become
obsolete.
ARTIFICIAL
DIAMONDS. Many experiments were made in the laboratory, for the
production of diamonds of which those of Moissan (1893) and of Noble
and Crooks (1906) may be briefly mentioned.
MOISSAN'S
EXPERIMENT. By his experiments, Moissan produced diamonds of
microscopic size by dissolving carbon—prepared by the ignition of
sugar, in molten iron and suddenly cooling the mass. The melting was
done at 4000°C. in an electrical furnace, when the iron melted and was
saturated with carbon. The crucible was then suddenly cooled in a
waterbath, which resulted in a solid crust and a molten interior. This
set up enormous pressures inside and the carbon crystallized as diamond
and graphite. The shell was then removed by dissolving it in
nitro-hydrochloric acid. The residue consisted of graphite and a few
colourless, transparent crystals. Moissan felt convinced that he had
produced minute diamond crystals, but it has been recently proved that
the crystals obtained were not diamonds. The method of Noble and Crooke
consisted in exploding cordite in an iron cylinder for a sufficient
period to permit the carbon to be liquefied, and then solidify in the
crystal form as diamond. The explosion generated a pressure of 50 tons
per square inch and a temperature of 5100°C. Minute crystals were
formed, the largest being only 0-5 mm. in length. The success of this
experiment has also been questioned. The iron meteorite of the Canyon
Diabolo from Arizona is said to have contained minute diamonds. So far
no artificial diamonds have been manufactured for commercial purposes.
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