# A Treatise on Diamonds, and Precious Stones/Chapter 1/Section 1

A
TREATISE ON DIAMONDS,
&c. &c.
CHAPTER I.
Section 1.—Preliminary Observations.
BEFORE I begin to treat on the peculiar characters of Diamonds, it may be proper to enumerate the different shapes and forms in which they appear when polished. The first of these is termed the Brilliant, the next the Rose, the third the Table, to which may be added the Lasques. All these distinctions will be found fully explained in the section on cutting and polishing.
​It may also be premised, that, in speaking of individual diamonds, we often, for the sake of convenience, use the term stone, “a beautiful stone,” “a bad stone,” which, although not strictly applicable to this substance, is sanctioned by general usage.
Diamonds are sold by a particular standard, which appears to be universally adopted. The integer of weight is termed a carat, and it is divided into four grains. To prevent the vircumlocution arising from the use of two terms, the weight of a diamond is often stated simply in grains. The carat is divided not only into quarters, (or grains), but also into eighths, sixteenths, thirty-seconds, and sixty-fourths, and these minute subdivisions ​are ascertained by scales of the greatest nicety and exactness. A stone weighing two carats would be said to weigh eight grains, and one of four carats and a grain would be more briefly designated by the lower denomination, as weighing seventeen grains.
The commerce of diamonds is, perhaps necessarily, in the hands of two distinct classes: viz. the diamond merchants and the jewellers. The former are considered to be men of opulence, well acquainted with the nature and. properties of the gems in which they deal, and with the mechanical details of the manufacturing department. As their dealings are almost exclusively in large amounts, they may he said to be little known, except to the importers of rough diamonds, and to the trade, as distinguished from the public in general. The diamonds being manufactured, cut, and polished; or, to use the technical term, made, are ready for the jeweller, who selects such ​as may best suit his purpose; these being weighed, are sold to him at such prices, and on such terms of payment, as may be agreed upon. He then commences the operations belonging to his department or art; which is to arrange, display, and set the gems so as to produce the best effect, and present the most striking and captivating appearance, according to the nature of the ornament required: whether it be an elegant groupe, richly combined, a necklace, an ear-drop, a ring, or a pin. The setting should be as little shewn as possible, for it is by concealing his art that the jeweller displays the gem to the greatest advantage.
Having shewn the source from whence the trade is supplied with diamonds, it may not be improper to notice the state in which they are generally offered for sale to the public, and give some idea of the manner in which jewellers dispose of them.
​Diamonds, when well set, always appear larger than when they are loose, and this circumstance gives great advantage to the seller. Shallow brilliants, that have a great surface, are for this reason always in request, and are generally set close. Thus a stone of only a carat may appear as large as a well-proportioned stone of six grains,
The smallest flaw, or foul, (as it is called) greatly diminishes the price of the diamond; and if it be tinged with yellow, brown, &c. a fault characterized by the technical term off color, its value falls very considerably, and is frequently reduced from a third to one half. To counteract these defects, and to conceal the appearance of what are deemed imperfec​tions, great ingenuity is exercised, and often with success, so that an inferior stone obtains the price of a perfect brilliant. It rarely happens that the purchaser of a suite of jewels is acquainted with the circumstances incident to diamonds, and from this inexperience and want of sound judgment on the qualities of the article, he is obliged to rely implicitly on the good faith of the person with whom he deals.
It may here be observed, that from the great value attached to diamonds, and from the universal desire of the opulent to possess them, various compositions have been manufactured in imitation of them. As these imitations, however, are unable to sustain a rivalry with the pure brilliant, manufacturers have succeeded better in endeavouring to form, with all the advantage of close setting, an imitation resembling bad, discolored, faulty diamonds, more especially rose diamonds; ​but let the composition be drawn from its glittering cell, and it will fade into insignificance before the real gem, which, with its vivid flash, will so forcibly appeal to the eye, that even an inexperienced observer must feel ashamed of having been for an instant deceived,
White topazes, and rock crystal, have been exposed for sale as diamonds, and glass has also been made into peculiar forms, to resemble the rough gem. These deceptions have often been practised abroad, and sometimes with success.
Persons accustomed to inspect diamonds, judge of them, when close set, from the perfection of the facets and the sharpness of the work. Yet, though an experienced judge may, in this case, pronounce with tolerable certainty on the nature of any specimen shewn him, I consider it best to withhold an opinion ​of any stone when close set, and not to decide until it is taken out, as the most practised eye may possibly be deceived by the various artifices of placing foil, patching that foil coloring, &c. The most simple and best method of determining whether a substance is diamond or paste, is to apply a very fine file to the girdle, which produces no effect upon the diamond, while paste or composition are easily abraded by it; and if the girdle or projecting angle of a diamond be applied to stones which deface the file, as white topaz, sapphire, &c. it will instantly cut them, the diamond having no rival that approximates to it in hardness. But it is by no means advisable to apply this test with a valuable diamond, as it might possibly produce a flaw.
​Other means of distinguishing diamonds from inferior substances, though highly useful, such as the polarisation of light, electricity, specific gravity, combustion, &c. can rarely be resorted to, except in the laboratory of the philosopher, and are little available to the purchaser of diamonds. The safest and most efficacious criterion for detecting flaws in brilliants, or, in a word, faulty diamonds, is tact, resulting from vigilant attention and habit,
* ↑ The carat is an Indian denomination of weight. One hundred and fifty carats and a quarter are equal to an onnce, Troy.
* ↑ A brilliant is said to be close set, if the setting has a back; it is said to be open, au jour, if it has no back. Fine brilliants are always set open.
* ↑ Glass or stones, set with foil, reflect its color; those which are intended to imitate diamonds, when looked at attentively, always appear too white.