All About Imitations, Improvements, and Reconstruction of Precious Stones

Counterfeiting precious stones of the higher classes has the same motive as counterfeiting coin or paper money, and is easier, because gems have no official characteristics, the physical and chemical characteristics are known to but few, and the counterfeiter does not hazard the penalties that the stringent laws of all nations enact against counterfeiters of the currency, the deterrent and punitive effects of which, however, despite their severity, have never entirely prevented successful counterfeiting. The counterfeiter of precious stones, and the dealer who knowingly and deceptively sells his product for an undue profit, swindle, and they are amenable to the criminal and civil laws, if evidence can be secured upon which to base successful prosecution and suits, a difficult matter generally, especially to prove guilty knowledge and intent. An enormous quantity of imitation gems is constantly being manufactured and sold under various qualifying terms that preclude the possibility of the purchaser establishing a claim that deception was practised, and in most cases the price paid was far from that which a genuine stone of equal weight would bring in any market. These imitations frequently bring to their buyers one disappointment, in that their brilliancy soon deteriorates or fades almost entirely. Sometimes "diamonds," which are qualified with such prefixes as "Alaska," "Sumatra," "Borneo," or any other name dictated by the dealer's fancy and which, it is hoped, will sound to the ear of a possible customer like a locality where diamond mines might be, are quartz or some other simple mineral; but in general they are of glass that has long borne the time-honoured name of "paste." Merchandise of this peculiar kind is so favourably exhibited in show windows and showcases by electric lights and other advantages, as to deceive the inexperienced prospective buyer. By the merchants who offer for sale these transparent imitations they are called "white stones."

Every gem for which there is a considerable demand has been, is, and, probably, always will be, imitated. Another name for "paste" is "strass," derived from a man named Strass of Strassburg, capital of the province of Alsace-Lorraine, Germany, who invented one of the several formulae and processes employed to create the brilliant, heavily lead-impregnated glass so enormously used in the counterfeiting of gems. While the many prescriptions for the strass composition vary in constituents and proportions, a fair sample of these mixtures is as follows:

Pure powdered quartz 38.2

Red lead 53.3

Potassium carbonate 7.8

The ingredients are pulverised, mixed, and heated in a crucible with a temperature raised gradually until the compound fuses, with great care. It is maintained at that point for about thirty hours and then slowly decreased. The factors in securing a result that will fulfil all requirements are the thoroughness of the previous mixing, the regularity of the temperature, the duration of the fusion, and the slowness of cooling. The clear paste is cut for imitation diamonds, while for the coloured gems the hue desired is imparted by the solution of metallic oxides and other substances; manganese oxide being generally used for the ruby and cobalt oxide for the sapphire and amethyst, while copper oxide is also used for the amethyst and emerald, with traces of chrome oxide also, for both these stones; glass of antimony is also employed in colouring imitation rubies, topaz, garnet, amethyst, and aquamarine.

The simplest proof that these sophistications are glass is the employment of a file, the use of which could have no effect upon the diamond or upon any precious stone harder than quartz, unless by some rough handling a fracture might be caused. Such a fracture is particularly liable to occur at the girdle, the thinnest part, where the test is usually applied because the result would not there be visible in a set stone. Besides their comparative softness, these counterfeits differ in specific gravity from genuine gems, they are not pleochroic as are the majority of gems, and the microscope reveals the lines, streaks, and bubbles usually present in melted glass. True gems are colder to the touch than glass, as a rule; although this distinction might prove too fine to be relied upon by the inexperienced. As gems are better conductors of heat than glass, they abstract the warmth from the hand more rapidly, and for this reason also gems, when breathed upon, acquire a thicker coating of moisture than glass and lose it more quickly.

In the advance chapter from the Mineral Resources of the United States-calendar year 1906 of the United States Geological Survey, entitled, "The Production of Precious Stones in 1906," by Douglas B. Sterrett, appears a valuable suggestion for a simple method of testing some precious stones, made by Mr. M. D. Rothschild, a recognised authority on gem minerals (this extract was republished from The Jeweller's Circular-Weekly, of January 16, 1907):