A Treatise on Diamonds, and Precious Stones

Front matter

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TREATISE ON DIAMONDS.

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Chapter 1 : On the Diamond.

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TREATISE ON DIAMONDS,

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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,

SECT. II.

Commercial Value of Diamonds.

In the great or wholesale trade there is but little fluctuation in the price of those diamonds which may be termed stones in general demand. I will begin with brilliants, from a

grain, to two and a half grains each. Such brilliants, double cut, and what may be termed fine, are worth from seven to eight pounds, per carat. Needy sellers may take ten per cent. less for cash; but this is the general average price for a lot of ten, twenty, or fifty carats of well-made stones, if the quality be good.

Brillliants, from two grains to three, may be bought m lots, at from seven guineas to eight pounds, per carat. It is to be understood, that diamonds in a lot are never all quite free from faults, hence there may arise a difference of ten per cent. in the price. Stones of three grains, if fine and perfect, are always in demand, at eight or nine pounds per carat.

Brillliants, from three grains to four, if very fine, and well proportioned, are worth from eight guineas to nine pounds, per carat, Those of a carat each, if very fine, and well selected, are now worth nine guineas to ten pounds. Three years ago, I offered twelve pounds each for eight, and could not obtain them.

Brilliants, from five grains to six, if pure, are worth from thirteen to fourteen pounds; if perfectly fine, and of the full weight of six grains, they are worth seventeen to eighteen pounds each; I have, for such, paid twenty pounds.

Brilliants of two carats each, are worth from twenty-seven to thirty pounds, Stones of this weight, if well proportioned, are considered of a fine size, and well calculated for pins, or the centre of clustres. Indeed, well proportioned diamonds from six grains to two carats each, are always in demand, and are retailed at from twenty to thirty-five pounds, each, according to their degree of per- fection, or as the retailer may think fit to charge them,

For brilliants of three carats, if tine and well formed, from seventy to eighty pounds may be obtained. Stones of this size and larger are more liable to capricious fluctuations of price than the smaller ones before named, being chiefly required for the centre stones of saleable necklaces,

Brilliants of four carats, if fine, are worth from £100 to £130. I have sold stones, single cut, a little off color, of this weight at eighty guineas. I possessed one of seventeen grains, perfectly white, having a surface as large as that of a seven carat stone ought to be, it was consequently very thin, but being much in request on account of its great spread or surface, it was sold for £160.

Brilliantsof five carats are not frequently met with in general trade, and are variable in price, as the dealers exact more if they know that such stones are wanted, than they would in the regular course of business. The prices may be said to vary from £180 to £200.

Brilliants of six carats, as before-stated, are not common; they are suitable for centre stones of expensive necklaces, and single stone rings: if perfect and well-shaped, they sell for £230 to £250, or more.

For estimating the value of peculiarly fine diamonds, there is no fixed standard; the rule already published may, however, serve as a sort of guide.

Rough Diamonds, selected as fine, and well formed for cutting, may be estimated as follows: Square the weight of the stone, multiply the product by two, and the result will be the value in pounds ster- ling. This rule, however, is by no means in general use. Brilliants, ifgfine, may be estimated by squaring the weight in carats, and multiplying the product by eight, which will give the amount in pounds sterling.

SECT. III.

Remarks on the Purchase and Sale of Diamonds.

The following observations may be found useful to those who are desirous of purchasing or disposing of diamonds.

I once possessed a brilliant of eight carats, well proportioned, and extremely fine, with the exception of two spots of what is technically called foul; one was in the centre of the table, not larger than a small pin's head, and the other at the corner of the table. It was sold for £380; but had it been quite perfect, it would have obtained from £550 to £600, or more.

The Nassuc diamond, valued at thirty thousand pounds, and which I modelled on its arrival in England, belonging to the East India Company, weighs seventy-nine and a half carats, and if it were a well-proportioned stone, and cut in brilliant, it would doubtless be much more valuable. This example may serve to shew, that it is not merely because the substance is a diamond that it commands a high price; but because, as a diamond, it must have all the qualities that art can bestow, and be faultless.

There is an extensive traffic in these precious substances, exclusive of the regular trade between the jeweller and the merchant. A person possessing a suit of brilliants may be inclined to part with them from necessity, or other causes. This occurs so frequently, that diamonds to a great amount are continually disposed of in a private way. If, as it frequently happens, necessity be the motive, a degree of caution and delicacy is to be observed, which renders any competition of pur- chasers impossible, and prevents the article from obtaining its true value. In this sort of confidential bargain, it is to be lamented that the seller is almost compelled to accept such terms as may be offered.

Some time ago, a person was obliged, or perhaps persuaded to dispose of a brilliant necklace that had been received as a gift. The lady applied to ___, in whom she had implicit confidence. The result of the interview was, that they purchased the article for a sum under £300. Being themselves in want of money, they took the stones from the setting, and sold them by weight for nearly double the purchase-money.

Another instance is within our knowledge of a lady having purchased a pair of ear-ornaments (tops and drops) for £250; after a lapse of some time she determined to sell them, and was only offered £60! She afterwards went to a Diamond Merchant, who weighed the drops, and offered £ 120 for them alone, which was accepted.

A lady became possessed of a brilliant necklace by legacy, on which it was necessary to pay the duty. A jeweller was referred to, who valued them at £1,600, and the duty was paid on that sum. The same neck-lace was soon afterwards disposed of, and estimated only at £800, in exchange for other articles!

It may here be observed, that the great difficulty which. presents itself to those who may be delicately situated, and wish to dispose of their Diamonds, arises from their not knowing that they are sold by weight. Diamonds free from flaws have generally a regular price: they are easily taken out of the setting, and a working jeweller would do it in a few minutes; but if the brilliants. are very thin it is the safest way to put them, fora few hours, in nitric acid, when they become loose by the acid dissolving a portion of the silver cramps that confine them.

Snuff-Boxes and portraits set with brilliants are generally composed of thin Diamonds, which present a large surface.

The fineness, as well as the weight of Diamonds, as before stated, must be considered in estimating their value. Suppose a half hoop ring to be composed of five stones, allow the centre one to weigh three grains; those next to it 24 grains each, and the others, 2 grains each: here would be three carats of Diamonds, which, if fine, would cost the retailer from £18 to £20, but if they were in any degree inferior, would not cost more than from £14 to £16,

To judge of Diamonds accurately, they should be laid loose in a good light, upon a sheet of white paper, on which their purity and brilliancy are bestseen, their proportions ascertained, and the tinges of color, specks, flaws, foul, &c. most visibly exposed. This is the proper and fair mode of exhibiting them for sale.

Peculiar shaped brilliants, calculated for ear-drops, sell at capricious prices and are always in demand. It may be remarked that a dealer going among the merchants to purchase stones of peculiar forms, and ofacertain weight, will have to pay in many cases ten per cent. more than if he boughtthem in the usual course of dealing.

Two brilliants, single cut but finely propor- tioned, came into my possession a few years ago, one of which was 174½ grains, the other 184 grains: they had the smallest possible tinge of yellow, and were therefore what is termed off color; one sold for £117, the other for £125.

A lot of brilliants, single cut, from one to two grains each, was consigned to me for sale. At the time I could not obtain more than five guineas and a half per carat. They were worth more, as rough Diamonds could not be bought and manufactured for sale at the same price. They were in a small degree off color, but would set to great advantage in jewellery.

A necklace was sent to me from Spain, for which I allowed £120: the diamonds had a large surface, and black spots appeared through the table to represent the collets. I was aware that they were very thin, and of the description called lasques. Taking the stones from their setting, I found that they were upon foil; many of them brown, and so thin, that the best were only fit for making rose-shaped stones: the others I sold as bort, and found it difficult to obtain their cost.

An apparently beautiful brilliant, of a pink color, was sent to me, which I estimated at three carats, A great price was asked, and would have been given; but on drawing the gem it proved to be lightly tinged with color, and set on pink foil.

A rough diamond of 15: carats, apparently very fine, was consigned to me, valued at £400, it was judged it would be offcolor. I sold it to a Dutch merchant for £280; its form was a very regular octahedron.

It often occurs that alarge rough diamond, of a brown appearance, is only bad in a parti- cular part—but from the high refractive quality of the gem, it appears discolored all over.

A Lot of eighteen most beautiful rich diamonds, all of very high lustre, was sent to me. They had a slight tinge of yellow, and weighed seventeen carats. The price asked was three pounds per carat; they were afterwards bought at forty-nine shillings, not one of them made a white brilliant; they were all off color, and it was doubtful whether they would be sold at a price to cover the cost.

Three rough stones were consigned to me; they weighed almost exactly 5 carats each, together 15½ carats, they were all fine, and would cut free from flaws; though one exhibited some indication of not being of the purest water. Their forms were favorable for cutting to advantage, and making spread stones; they sold for £120, which was considered an excellent price: they would weigh together, when made into brilliants, from 32 to 34 grains.

I received a large fragment of diamond, weighing above 12 carats: one end was foul and full of flaws; I split it off, and discovered the foul was owing to a triangular hole, the sides of which were covered with black earth.

Yellow brilliants, if fine, are generally extremely lively, and suit the purposes of the jeweller in composing fancy articles. When of from one to two grains, they are usually from four to five pounds per carat; being inferior in value to the pure gem. I have known a yellow brilliant of 7½ carats, to sell publicly for £240,

Brilliants tinged dull green or brown are much depreciated by such colors. Cloudy diamonds are also of little value; hut those of fine colors—pink, red, blue, or green, are eagerly sought for by connoisseurs,

Diamonds at this time are considered very low, there are many offered for sale but few buyers; consequently some lots of brilliants, in the hands of needy sellers, may be bought at ten per cent. below the present average price; observing, generally, that diamonds were considerably higher a few years ago.

Brown diamonds are often brought from India of considerable size and brilliancy, but they rarely sell for their cost: indeed, cloudy and bad brilliants, or roses, have scarcely any commercial value, although, however, they may often be highly estimated by the possessor.

Inferior brilliants may be bought very low; I have now a lot before me, in which are some of two grains, for which I would not give four guineas per carat, and roses of the same denomination may be bought at forty or fifty shillings.

Bad discolord diamonds are sold to break into powder, and may be said to have a more extensive sale than brilliants with. all their captivating beauty. In many operations of art they are indispensible; the fine Cameo and Intaglio owe their perfection to the diamond, with which alone they can be engraved. The beauty of the Onyx would yet remain dormant, had not the unrivalled power of the diamond been called forth to the artist's assistance, The carnelian, the agate, or Cairn-Gorm cannot be engraved by any other substance; every crestor letter cut on hard stone, is indebted to the diamond—This is not all, for without it blocks of crystal could not be cut into slices for spectacles—agate for snuff-boxes, &c.

In the breaking of Diamonds, bits, shivers, an eighth of an inch long, sometimes occur, which if properly proportioned are in demand and used for drilling holes in glass, china, &c.

Diamond merchants have adopted a very delicate and highly honorable method of offering polished Diamonds for sale—they employ confidential men, to take: brilliants of various qualities, in separate lots, to the trade; their weight and price are generally marked on the paper in which they are folded. If a particular parcel is found desirable, but thought to be charged too high, an offer a little lower may be made: in which case the intended purchaser is allowed to affix his seal upon the lot, until the principal is made. acquainted; then, if the terms are not approved, the employee returns with them, and requests the seal to be broken. Thus, during the negotiation, which often continues several days, thelot cannot be exhibited or hacknied through the trade.

SECT. IV.

Physical and Chemical Characters of the Diamond.

It is the object of the present chapter to point out to the reader such of the peculiar characteristics of the Diamond as may enable him to distinguish it from any other substance, especially in its rough state, and consequently to detect any imposition which may be attempted to be practised upon him.

Rough Diamonds occur under the most beautiful and regular geometric forms, their lustre and color frequently resemble Gum Arabic; they often exhibit a polished appearance, more particularly the brown stones, others are dull, indented, rough, shewing their Jamine, and some are round. If, as might possibly be the case, a stone of the latter description was shewn toa person who had never seen a Diamond, although he might not be able to decide what it was, yet after examination he would pronounce it to be very unlike, and very different from any pebble he had met with before.

The most common form of rough Diamonds is the octahedron, variously modified on the edges with planes, and low pyramids on each face of the triangles. The next is the dodecahedron, which occurs also variously modified, both on its edges and planes: others are flat and triangular (heliotrope),these are termed veiny, and being thin, are generally split and cut into roses. The rarest form is the cube. No substance in the Mineral Kingdom displays in miniature such beautiful variety of regular solids as the Diamond, which are as captivating to the connoisseur, as the finest brilliant can be to the wearer.

Generally speaking, the degree of polish which a stone is capable of receiving, depends upon its hardness. That of the Diamond, which renders itso difficult to be cut and manufactured, enables it to retain unimpaired the lustre which it has originally received.

Small particles, laid on a new anvil and struck with a hammer, will indent both, and in some. cases will not be broken. Yet with this intensity of hardness the Diamond is far from being: difficult of fracture: a slight blow often causes it to split, and the fine edge of a brilliant is frequently injured by clumsy workmen. I have, known one to be chipped by falling on a boarded floor.

A regular formed Diamond, iflightly struck in the direction of the laminæ, will split easily; indeed it admits of cleavage in fourdirections, and I possess a perfect octahedron formed by cleavage. Spheroidal Diamonds break with a rough fracture; these are generally called Diamonds of nature. The fracture of this gem is the criterion sometimes relied on by the overseers of the mines in Brazil. Whena stone is delivered to them of a rude appearance, both ill formed and of a bad color, they have recourse to the hammer, especially if it exceed in size the Diamonds usually met with; they hold it upon a hard substance, and give it a sharp blow, should the fracture prove distinctly lamellar they are convinced that it is a true Diamond. In the treasury at Rio de Janeiro, I noticed three or four flat pieces of a bad brown color, an inch long by half an inch in breadth, and about one eighth in thickness.—To this rough kind of experiment may be attributed the fragments occasionally met with.

Diamonds may be distinguished by the senses of hearing and feeling, in the following manner. If two diamonds be held between the fingerand thumb, and rubbed strongly together, a peculiar grating noise will be pro- duced accompanied with a particular sensation on the nerves in contact with them—Or, if a diamond and a pebble, of equal size, be rubbed together in the same manner, the diamond will not be easily moved, as its projecting surface will penetrate the pebble.

To ascertain the supposed phosphorescence of diamonds | have tried many experiments (described by authors) without any satisfactory result, nor have my friends had any better success, even in a single instance.

The combustion of the Diamond is a property very generally known. It burns with great brilliancy underaflame urged by oxygen gas; and if exposed on a support of clay to a strong heat, it may be totally consumed.

The following experiment is worthy of being recorded. A small portion of iron was put into a crucible with a fragment of a Diamond, and exposed to a strong heat; on examination the iron was found to be converted into steel.

Diamonds of bad color are often improved by being exposed to a certain degree of heat in a small crucible, or the bowl of a tobacco-pipe, surrounded in some instances with borax. It is necessary for the vessel to be closely filled with charcoal, to prevent the admission of air.

The Diamond possesses double refraction; which is rather difficult to discover., By friction it becomes electric, but continues so only a few minutes.

SECT. V.

Natural History, Localities, &c.

The places where Diamonds have been found in modern times are—the central and southern parts of India, the peninsula of Malacca, the Island of Borneo,and some mountainous districts in the kingdom of Brazil, more particularly Serro do Frio. In the latter place, which is peculiarly celebrated, they are found in rivers or rivulets, in the banks adjoining water courses, and in ravines. The Diamond is invariably found mixed with the alluvial soil. This soil constitutes a thin stratum of gravel, resting upon Granite. On the banks and in ravines, the stratum is covered with vegetable earth more or less thick. If quartz pebbles, clay slate, brown [ron Ore, and Iron Sand con- stitute the alluvium, they are considered good indications. In one part of the Diamond District the cascalho forms a solid breccia, cementation having taken place from the oxidation of the iron: in this mass Diamonds and gold are sometimes found enveloped.

To explain in a more particular manner the general locality of the Diamond, I will suppose a valley to be formed by mountains of granite; through which runsa rivulet, having on its margin gradually rising hillocks or plains, more or less distant from the base of the mountains. It is by analogy that the presence of the precious gem in such a situation is to be inferred, and hence a little geological experience is highly necessary. Diamonds having been found in ravines, formed by such mountains it is fair to presume that they may. occur in others of a similar character. For ascertaining this, the experiment is easy, and demands no expenditure of capital for excavating ground either by labor or machinery. The mining for Diamonds is a much more simple operation. The mode of proceeding would be as follows: I should endeavour to procure some of the alluvium from the bottom of one of the deepest places in the rivulet; or if any little sand-bank appeared dry, I should remove the sand and mud from the surface, and scrape the gravel up, continuing this operation until I came to the solid rock, which is seldom more than two or three feet below the surface, and frequently only a few inches. I should begin the examination by putting a shovel-full of it into a bowl, commonly called by the miners a gamella, which is about 18 inches in diameter, and 10 deep, of a conical form, tapering to a point; having filled up the vessel with water, I should agitate it with my hand in all directions, and, when the water became muddy, pour it off and add more to it, holding the gamella with my left-hand, and stirring the gravel with my right, repeating the change of the water, until the earthy particles were dissolved, and the pebbles clean washed. During this agitation, from the peculiar form of the vessel, the heaviest substances in the cascalho would have sunk lowest and remain undisturbed, the surface being in a tenfold degree more exposed to this sort of trituration than the bottom.— Having poured off the clear water and thrown away the stones from the surface, the remainder would require to be carefully examined; the diamonds, if any, being heavier than the pebbles, would be found at the bottom, and may easily be discovered through the medium of water, which gives them an additional lustre, so that they cannot be mis- taken. They are never found with any crust upon them, but their exterior being often rough, they have been many times improperly so represented,

If after continuing the examination for three or four days nothing of the kind was found, the place would be abandoned, without having occasioned five shillings' expense. If any of the precious gems presented themselves; methods would be taken to wash the gravel of the rivulets, and the banks, to the very rocks, on an extensive scale. It was by the above mentioned process, that the adventurous Portugueze, after penetrating into the interior, where they had to contend with the Anthropophagi, discovered their diamond and gold mines.