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Ch. 17: Synthetic and Imitation Gems

Ch. 16: Buying and Selling Page of 96 Index Text size:minus plus Restore normal size   Mail page  Print this page
GEMS AND PRECIOUS STONES.
Imitation Gems.
The art of making imitation precious stones has reached a high state of perfection, and there is in the Technological Museum a remarkably good set of these "paste" gems. The manufacture has been carried on for a very great number of years, and no doubt often with great profit, as many of the supposed gems which used to embellish European churches are without doubt " paste." The imitation gems are usually made of a material called strass, composed principally of the very best glass, with a large percentage of lead to give lustre, and different metallic oxides to impart colour, as cobalt for the sapphire, chromium for the emerald, &c. Their detection is not difficult, as they are comparatively soft, all yielding to a file ; have a high specific gravity, and are not dichroic like many real gems.
Artificial Gems,
A distinction must be made between imitation and artificial gems; the latter are made by taking the same component parts as are contained in the real gem, and then by great heat or other methods, forming a stone having the same composition, hardness, and crystalline form as the real gem. As yet marketable stones of the most valuable gems have not been made, although minute diamonds, rubies, and sapphires have been artificially manu­factured, and good sized spinels have also been made, which could not be distinguished from natural stones. The tendency of the higher chemistry to-day is towards synthesis rather than analysis, and the progress of the science will no doubt overcome the problem of the manufacture of the better class gems, of saleable size and quality. It is problematical whether the diamond will be made of sufficiently large size to be of value commer­cially, although from a scientific point of view the making artificially of the minute octahedron of crystallized carbon, is an accomplishment one may well be proud of, especially as it breaks down another barrier between the scientist and the secrets of the laboratory of Nature.
Ch. 16: Buying and Selling Page of 96 Index
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