Can You Pick True Gems from False? newspaper article

Can You Pick True Gems from False? newspaper article

The chemist can match nature in the production of many gems - and the chemist works faster.
It may not be long before you can have buttons of real emeralds, and stud the dog's collar with sapphires.

By APRIL McKEE-WRIGHT.

THE chemist has caught up with nature. From the laboratory now come synthetic emeralds, rubies and
sapphires created by a process which makes them, in truth, real gemstones. Exquisite beauty and craftsmanship are now within reach of everyone. Lovely, durable and fresh, the laboratory-made gem is yours for shillings, where the gemstone crystallised through millions of years, often flawed or discoloured, is worth pounds, more often hundreds of pounds.
THE new gems are not just paste and glass, which can be detected easily by their colour, nor doublets and triplets. In a doublet, the front is real and the back paste. In a triplet, the front and back are real, but to add depth and colour to the stone the centre is paste. They will fall apart if dropped into chloroform. sometimes even in hot water, which melts the cement mixture binding them.
Synthetic diamonds have not yet come, but very small ones have been constructed. The substitute is the white sapphire. Though almost as rare as the diamond and as highly priced, there is a difference. Diamonds are pure carbon. OTHER stones are mostly either alumina or silica, or a combination with other components. Sapphires contain iron oxide and titanium which is believed to give them their dark blue colour. Nature's workshop takes, millions of years to produce these exquisite crystals. Now. chemists know the ingredients, and taking them in a powder form which is then submitted to intense heat, they can actually create the sapphire. In all essentials it is the natural stone, and only the expert can. tell them apart. A hundred years ago the Chinese began experimenting with artificial gems. It was known that the blood red colouring of the ruby was the result of aluminium oxide plus chromic oxide. But that is as far as their tests went. Verneuil, a chemist, after a number of unsuccessful experiments, fused oxide of aluminium, and developed the process until rubies, large, and of a good colour were made.
But though this began the industry, and one workman, operating ten furnaces could produce thirty carats an hour in one furnace, it was not until Verneuil discovered the vertical oxyhydrogen blowpipe, and the tremendous heat of an earth age in which the original stones had been formed was recreated, that the making of artificial gems became really practicable. Later, by using this same blowpipe, spinels were made into gemstones. SPINEL, in mineralogy, is the name given to a group of minerals which crystallise quickly. They vary widely in colour. Magnesia spinels are pink, red and blue, and these are the ones used in jewellery. About 20,000,000 carats of rubies and 12,000,000 carats of sapphires are produced annually, from spinels.
The best of these gems now come from Czechoslovakia but . they can also be made in Australia. Since 1905 the production has increased until to-day they are called the jeweller's headache. Culture pearls are comparatively modern. These are produced by introducing an obstruction into the pearl oyster. They are usually much smaller than the real pearl, and gem experts can pick them also by weight. The man-inserted obstruction is often larger than the natural one, to increase the size of the pearl and shorten the production period. Real pearls can be separated from glass or plastic by placing them between the teeth. If they feel gritty they are real.
No stone can be checked thoroughly unless it is taken out of its setting. The simplest test is by colour.
Roughly, ferric oxide produces yellow, ferrous oxide the bottle green tint; red is due to chromium and blue to iron oxide. Some colours fade when the stone is exposed to sunlight. Pink is particularly fugitive. Yet heat will induce great changes in colour. . Applied to certain yellow aquamarines, it will turn them a delicate pink. And the colour of brownish zircons can be removed by heat, when their brilliance and fire resembles the diamond. Natural emeralds are now very rare, and olivines are passed for them. The emerald has a peculiarly olive-green sheen, not present in the olivine or in imitation emeralds. The beryl is a sister stone to the emerald, but is a golden yellow.
THERE are a few stones that have never been duplicated, and probably never will be. The Australian opal is composed of silica and water, and it is the interference of light within the stone that causes the peculiar iridescence. No chemist can produce that-yet.

The Sunday Herald
Sunday 27 February 1949
http://newspapers.nla.gov.au/