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Artificial Diamonds

( Originally Published 1911 )

There have been many attempts to make diamonds. The difficult problems involved have excited the desire of scientists to solve them and the great value of the gem has been an incentive to hundreds who experimented in the hope that they might learn how to turn one of the common elements of the earth into costly jewels. Stimulus was given to these endeavors by the discovery of the diamond chimneys of Africa. Occurring there in the mother-rock, it was thought that clues might be obtained to the processes by which Nature accomplished the crystallization of carbon, but so far, of all the theories evolved by observation and experiment, those which were in any degree carried to a successful issue, demonstrated more forcibly in practice the insufficiency of man's appliances, than his ability to compete with Nature.

Carbon, unlike many elements, occurs in Nature uncombined with others and in three forms ; as graphite, carbonado and diamond. In combination with others, it appears as a solid in minerals, a semi-solid as in vegetation, a liquid as in earth-oils, and a gas as in carbonic acid. At a high temperature it vaporizes without liquefying, and in the presence of oxygen at a high temperature combines with it to form a gas, the union being accompanied by light and heat. The problem has been, how to separate it from its affinities and establish it as a single element in the stable crystalline state.

Probably the first definite theory 0n record of the origin of the diamond is that 0f Sir David Brewster, who believed that the diamond was at one time viscous like a resin, and that its formation came from the vital processes of plants, as tabasheer, a form of silica, grows in the stem of the bamboo. This theory was accepted by later eminent mineralogists and physicists. Others adopted it with various modifications. Some thought it a product of the decomposition of extinct plants by which, through the evaporation of the decomposition products, pure carbon only was finally left, and that this eventually was transformed from an amorphous to a crystalline state. This theory assumed that the processes were evolved at a low temperature, as graphite would result from high temperature.

Others thought that heat was necessary, and that small particles of carbonaceous matter, contained in an igneous rock or taken up from neighboring sources during the passage through them of a volcanic magma, crystallized out as diamond as the mass cooled.

Several thought that large quantities of carbon dioxide in the interior of the earth were reduced at a high temperature by other metals present, the pure carbon crystallizing in the process. From the fact that liquid car-bon dioxide is supposed to exist in cavities in some diamonds, one scientist formed the opinion that liquid carbon dioxide at a high temperature and under great pressure, would dissolve carbon, and that diamond might crystallize out of the solution. Experiments in this direction, however, failed to dissolve the carbon.

Liebig thought that pure carbon in the crystallized form was the final result of the gradual decomposition of a fluid hydro-carbon at a low temperature. Another scientist claimed that such a separation could only take place by the action of heat. One thought that the diamond crystallized out of carbon volatilized by volcanic heat, and yet another was of the opinion that it was formed from an excess of carbon during the oxidation of the emanations of a gaseous hydro-carbon.

The decomposition of various mineral compounds of which carbon was a constituent, is believed by many to have been the method by which, during the chemical reactions, diamond was precipitated as a crystal. Others discredit the solution theory and maintain that it was accomplished by the interaction of gases.

Professor Moissan, the most successful experimenter, obtained diamonds by a combination of heat and pressure simultaneously applied to a solution containing carbon. Knowing that molten iron was a good solvent for carbon, he took iron filings and charged them with pure sugar charcoal. Placing the mass in an electric furnace of his own construction, in which he was able to concentrate the energy of 100 horse power upon the crucible, and produce a temperature between 6,000 and 7,0000 F., he melted the carbon-charged iron to an ingot. When at this tremendous heat the iron began to vaporize, he plunged the seething metal into water or molten lead, solidifying the outer skin of the ingot by the sudden cooling, about the still liquid interior.

Cast iron, though it contracts later in cooling, expands when it solidifies and the expansion of this liquid interior within the rigid shell, as it solidified, produced an enormous pressure. When the iron was eaten away by repeated acid baths, there remained a number of crystals, microscopic, but veritable diamonds; the car-bon had crystallized. The largest crystals he obtained, however, did not exceed / millimeter in diameter. Of all the numerous experiments made so far, if others have resulted in crystals or crystalline masses which were apparently either diamond or something very like it, un-questionably genuine diamonds have been produced by this method only, though I. Friedlander demonstrated, it is said, that graphite is soluble in fused olivine, and that it separates out as diamond on cooling.

Electric sparks passed through a vacuum with a car-bon cylinder and a platinum wire as terminals, for over a month, coated the wire with microscopic octahedra which were said to scratch corundum. A crystalline mass containing ninety-seven per cent. carbon was obtained by placing lithium, paraffin and a little sperm oil in a sealed wrought-iron cylinder and subjecting it to a very high temperature.

While scientists at a cost of much time, labor and money, have patiently studied and experimented, in the effort to crystallize carbon, charlatans and rascals have been busy deceiving the gullible, Not many years ago a dealer in imitation gems was very successful in selling glass diamonds by adopting the idea of gold-plated jewelry. He announced with a great show of frankness, that his diamonds were not diamond throughout, but that a piece of very fine crystal glass was used for the body of the stone. This was dipped into a liquid made of melted chips of diamonds, whereby a coating of diamond was deposited on the surface. The finished product was therefore practically as good as solid diamond, though the cost was very much less. Having in mind the well-known process of plating the base metals with gold, many persons paid large prices for his pure glass diamonds, and not a few jewelers also gravely and innocently retailed the story with his high-priced glass gems.

Paste diamonds, or glass, as they really are, have been sold under many names. " Paste diamonds " or white stone jewelry " are names used when there is no attempt to deceive, but many of the names given to these imitations, though unaccompanied by explicit false statements, are intended to aid the buyer to infer that they are better than they really are. Most of these, since the greater vogue of the diamond in this country, have fallen into disuse, as the " Lake George diamond," the " Colorado diamond," and the " Parisian diamond." A few years back, stores filled with cheap imitation diamonds with which pieces of so-called white topaz or rock crystal, cut like diamonds, were mixed and placed under effective electric lighting, were opened in most of the leading cities of the United States. Ambiguous signs carried an impression that the imitations were either real stones, or so superior that they were preferable to stones that were real. In some cases it was stated that real diamonds were placed among the imitations and if picked out by a customer, could be bought at the same price. The nominal price of the jewels displayed was one dollar each, but a customer willing to be enticed could easily pay much more for a piece of the same value, for some fancied superiority. So cleverly were these glittering displays managed, that sufficient profits were made out of a foolish clientele to pay the high rentals of stores in the most expensive locations, and leave a large surplus for the managers.

In the past, white sapphire, jargoon, white topaz, and rock crystal have all at times been sold occasionally as diamond, but of late years imitation diamonds, of what-ever name, have been simply glass, for fine specimens of sapphire and jargoon excepted, glass looks better long enough to sell, than the other stones which though real, are not as deceptive.

As enormous quantities of them are used, much ingenuity has been displayed in the manufacture of glass diamonds and the art has been brought to a high state of perfection. The imitation of gems is as old certainly as Egypt, but the fine white glass composition which with some variations is used now, was invented in the seventeenth century by Josef Strasser of Strasburg, and was called after him " Strass." It was composed of silica, potash, borax, red-lead and sometimes arsenic. Of the different proportions used now, the following is given as a good example : 300 parts powdered quartz, 470 parts red-lead, 163 parts potash (purified by alcohol), 22 parts borax, I part white arsenic, by weight, This makes a dense white glass and is the mixture called strass or paste, from which the fine imitations are made. Great care is exercised in cutting the fine imitations, not only in the work of faceting, but also in shaping and cutting to proportions which will hide as much as possible the inherent differences of reflection, refraction, and dispersion. Though one familiar with diamonds cannot be deceived on inspection, under some conditions when worn, a fine paste will escape detection. The surface brilliancy is often very beautiful. Though it will not entirely hide the internal weakness and vacancy of glass when at rest, it is confusing when in motion. In order to hold the light entering the stone from passing out at the back, which gives a glass diamond its weak, lack-luster appearance when at rest, the back is sometimes entirely covered with foil. These are used for close-set jewels, in which the backs of the stones are not seen. For openwork setting, the foil is put on and just around the culet. But these are not popular except in cheap gold jewelry, as the foil at once betrays the imitation even to the inexperienced, and most of those who wear paste jewels are at least willing that the observer shall have a chance to believe them real gems.

Paste diamonds are not as ancient as imitation colored stones. The Egyptians, Phoenicians and Romans were adepts at manufacturing spurious emeralds, rubies, and similar stones, but they did not imitate the diamond. Perhaps no better evidence exists of the late recognition of the diamond as a jewel than the fact that it was not imitated prior to the seventeenth century. Since then paste has glittered on the persons of thousands who loved, but could not afford diamonds, and has shone from the buckles and belts of many who though rich, thought them good enough for certain purposes. Years ago the jewels of the stage were well-nigh all glass, but now popular singers and actresses wear gems both rich and rare.

Look into a paste diamond from the front, and it will be seen that the inner surfaces of the back facets lack the shimmer of light on them which is so noticeable in the real diamond. The surface of the stone nowhere looks so hard; the corners of the facets are not as sharp ; the light from it is not as quick and sharp. Let a diamond and a paste lie together in the same temperature for a few minutes, and it will be found on touching them with the tongue, that the paste feels warmer than the stone. Touch the face of each with a point carrying water, and the drop left on the diamond will hold itself together like a globule; that on the paste will flatten and spread. The sharp edge of a file will bite the imitation, but glide harmlessly over the diamond.

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