ARTIFICIAL DIAMONDS.

Lyttelton Times, Volume LIII, Issue 5950, 22 March 1880, Page 5

ARTIFICIAL DIAMONDS.

(Prow tl i« Doily New*, iTon. 9.) The controversy, or rather investigation, now pending as to the recent manufacture of actual diamonds has produced no little excitement among the. holders, of and dealers in precious stones. When Mr M'Tear, of the ,8t RoUox Works, (Glasgow, thought he had achieved the artificial production of the diamond, the first step taken by that gentleman was to court the fullest enquiry into the nature of his discovery. For the present opinions are divided as to the identity of the substance produced by him with genuine diamond. Testimony varies as to the actual hardness, the fusibility, and other qualities of the manufactured article.; In justice to the experts to whom specimens have been submitted, it is only fair to state that the frag-

moDtibfitoppowddiinnond hithertoniaslo at. St Bollox are very sradl, so minute, in fact, as to ca>se some difßuuity to the investigator. Mr Nevil Story Masielyne, a scientific mineralogist of high reputation, at the head of his department in the British Museum, expressed himself, after a first trial, ea clearly dissatisfied with the claim- ,of the substance experimented upon ‘t» the character of the diamond. Mr Maetried the supposed diamond or diamond dust by a triple test assumed to be Conclusive. Firstly, the diamond excels all substances in hardness, being reckoned at 10 for hardness, while other precious stones, such as sapphire, ruby, emerald, topaz, and garnet, are represented by gradually diminishing numbers. Thus a diamond justifies the popular saying by being the only substance which will cut a diamond, and as a matter of course, every softer gem-. Secondly,'the crystals of the diamond belong to the cubic system, and should not, therefore, posses* the property of doubly refracting- light, albeit accidental causes, producing strain Within, the crystal diamonds are not entirely without action on a ray of polarised light being sent through them. Thirdly, the diamond is pure carbon, and, as such, bums entirely awaj when heated to a sufficiently high temperature in the air, and more vividly so burns or glows away when heated in oxygen gas. It may he added that no solvents, not even acids, have the slightest power to dissolve or decompose the diamond. In thir it is distinguished from other precious stones, moat which, having silica in their composition, cannot withstand the influence of hydricfluoride.

Mr Maskelyne found that the particles of St Sollos diamonds did not scratch topaz, that they did act in the manner, of alrirefringent crystal, and that they were not fusible by the intense heat of a table blowpipe. uennine. diamonds submitted to similar heat disappeared, while the particles from Glasgow remain intact.. Satisfied by these experiments that the particles were; not diamonds, Mr Maskelyne, endeavouring to find out what, they were, ' heated taea oh platinum ’ foil , several: times .with, ammonium fluoride until they became visibly more minute, and a. slightly reddish-white incrustation was seen bn the foil. Then the particles were left for the night as hydrofluoric acid in a platinum capsule; By the morning they had disappeared, having become dissolved in the acid, and Mr Mkskeljyae' pronounced Mr MTear’s diamonds not, only not to be diamonds at all,, but to Consist of some crystallised silicate. Since this opinioh'wae pronounced Mr Maskelyne has seen Mr M‘Tear, and found a portion of the material he has produced bear out his claim as to it* excessive hardness. ; It is also understood that Mr M’Tear claims simply to have produced a crystalline form of carbon, irrespective of the question whether it is an actual diamond.

Meanwhile Mr M'Tear, not prepared to abide by the opinion of Mr Maskelyne alone, has submitted specimens : of St Bollox di*monde to several experts engaged in the diamond trade, who report that fine particles submitted to them act in all respects like true diamond dust. Moreover, the .inventor of the supposed crystallised carbon is about to ask the opinion of that eminent mineralogist^ , Mr Tennant, who pronounced authoritatively against the artificial sapphires brongbt to Jxmdon not long since, dhese; sapphires were of a fine blue colour, and counterfeited the appearance of the real gems almost as accurately as did the emeralds ..produced about, the same time. By no means originally made for the purpose of fraud a BVof the artificial sapphires came into the of a dealer, who, somewhat in doubt of his own expertnert, invoked .toe superior skill of Mr Tennant, who, by testing tha supposed gems for hardness and specific gravity, at once pronounced them spnriow. The precise composition of these well mads imitations of sapphire and emerald was not, it is believed, made the subject of prolonged investigation. The matter,, like the »up- , posed discovery of a method for making , rubies, died out of'public attention very i quickly without stimulating curiosity libs i toe experiments of Wohler and, Bevills, i which it was once thought might exorcise- , serious influences upon toe diamond trade. . Nothing less was threatened than toe for- ' mation of bodies akin to the natural carbon diamond, but consisting of the element > boron. Wohler and Deville, while faying to produce in large quantities' pure alamiinum, discovered a method of crystallising sOieon and boron. The crystallised boron showed in so remarkable a manner the properties o£ toe diamond—its hardness, transparency, and refraction—as to suggest an intimate relation between the two. The element boron, in combination with oxygen, forms boracie add, just as the carbon with oxygen forms carbonic acid. There is surprising similarity between toe elements boron and carbon ia the conditions of their existence, .anji .BQ far, as ia known, in the modes of origin of these form*. So far, however, aslexperimebt has gone it has only proved that the “ scare” produced for the-moment was not due to any serious cause. It has only been possible to produce boron crystals—which in that particular resemble the St Bollox diamonds hitherto, presented for inspection—of small size, and therefore of ho value as ornamental stones. The boron crystal has therefore never replaced, nor in any way approached the value of the diamond. What the St Bollox diamond may do remains to be seen. . It is not of the experiments of sclentifie chemists that the publioneed beware in the matter of artificial gems, but of the cunning workmen of Paris, Brussels, and the purlieus of Soho, London. It is not pretended that any serious frauds are perpetrated by toe aid of toe well-known “straes” or “paste” diamond, a recognised article of commerce in this as in the last csntuty, and .worn, even by day, by many vain persons in apparent unconsciousness that their harmless deception is easily detected in sunlight by the naked eye. Sham rubies and emeralds made of “ strass,” coloured with purple of oassius oc oxide of copper, and sapphires owing their hue to oxide of cobalt, are also not apt to deceive any but the most unpractised eye; so the lapidary who works “with intent to deceive” makes him a “doublet” or “triplet,” the latter being considered the highest form of his peculiar art. The “ triplet ” is in fact a sandwich stone, of which the outer slices are made of rock crystal and the middle piece of coloured glass or . composition. Thu emerald or sapphire thus constructed is of fine colour, and, when mounted, likely to impose upon all but experts. In mounting his sham sapphire, which may be worth from 30 to 50 shillings, the workman conceals the double join at the “ girdle ” of the stone, and thus presents two surfaces, both of which, resist the file—the common test of precious stones among those least acquainted with them. When the sapphire is set in the middle of a ring, the too-cunning operator sets a real diamond worth £4 or £5 on either .side of it. Having now laid out £l2 or £l4 upon his venture, he betakes himself to the seaside if it be summer time, or to a country town in winter, and finding himself suddenly short of money, essays to dispose of his ring, which, it is unnecessary to say, was given him by his mother. .He undergoes great grief at being, compelled to part into - such a precious relic, but has no choice, and therefore confides it to, a newly-made friend—who thinks it a bargain to get a ring worth £BO for £4O -or else tries his hand on that more difficult personage, the country pawnbroker, who, seeing the diamonds to be real and having tested the sapphire, ia now and then taken in by the reduced foreign gentleman, the exile in temporary straits, or by his mow - flashy English confederate. . Tricks of this kind have made timorous people shy of all precious stones but diamonds, which not many years ago were frequently bought as a safe and portable investment. But since tha influx of African diamonds, some of which, are of such fine size and quality as to sell for £3OOO or £4OOO a piece, the confidence of investors has received a rude shock, and purchases are not likely to ho accelerated until the fear of the last chemical discovery has passed away, Yet, should, even the particles made by Mr M'Tear prove as good as he thinks them, the value of fine gems is not likely to be affected, unless indeed he should succeed in excelling the experiments, of Wohler and Deviile, not only as to quality but uto else. ; •