The valuation of a diamond, involving as it does a nice appreciation of the defects and of the good points of the stone, and the striking of a just balance between the two, is a matter of no little difficulty, and can only be performed with accuracy and rapidity by an expert. In this section we shall confine ourselves to a consideration of the value of diamonds, which are to be used as gems, selecting those to be applied to technical purposes, the value of which depends on the weight and the current market price.
Of all the characters, which help to determine the value of a diamond there is perhaps none more potent than that of size. Other things being equal, the larger the diamond the greater its value, and, moreover, the ratio of progression in price is greater than that of progression in weight, owing to the comparative rarity of large stones. Since the discovery of the South African deposits, however, this disparity has been less marked, and the value of stones not exceeding a certain size and which are of frequent occurrence, is influenced to a large extent by the exigencies of the trade. Exceptionally large and beautiful stones, the so-called solitaires, paragons, or nonpareils, have, corresponding to the rarity of their occurrence, an exceptional value, which is subject to no rules and is governed solely by the special circumstances of the case.
The value of a diamond depends very largely upon the form in which it is cut. Although during the process of cutting the weight of a rough stone is reduced by one half or even more, yet its intrinsic value is greater than before, on account of the almost immeasurable improvement in its appearance effected by the faceting. The brilliant is by far the most effective form of cutting, and at the same time is the form, which involves the greatest expenditure of skill in the cutting, hence a brilliant-cut diamond commands a higher price than a rose or indeed any other form. Among brilliants themselves different degrees are recognisable, a stone which is correctly proportioned and which bears a large number of facets having a greater value than one less admirable in these respects. A brilliant which possesses no cross facets, the large facets being produced until they meet in the girdle, is described as being” once formed”; while the terms” twice formed” and” thrice formed” are applied respectively to stones which bear cross facets only below the girdle, and to those which possess these facets both above and below the girdle. The value of a brilliant, therefore, is the greater the more complex is its form of cutting, and in the same way the value of stones cut in any of the other forms varies with the symmetry and completeness of that form. A perfect brilliant of one carat has at least four times the value of a rough stone of the same weight and quality, and five-fourths the value of a rose of this size and quality.
The value of a rough stone also is influenced to a certain extent by its form, for, as we have seen, stones whose form in the rough approximates most nearly to that of the cut stone are most favourable for cutting. Thus octahedral and rhombic dodecahedral crystals can be fashioned into brilliants with less labour and loss of material than is the case with irregularly shaped stones, which often need considerable preliminary shaping, if not actual division into portions suitable for cutting. Among such stones must be included flat specimens, like the twinned crystals shown in Fig. g and h, which cannot be cut of brilliants and are suitable only for cutting as roses. Another property, which greatly facilitates the process of cutting is that of cleavage; a simple crystal, from which the cleavage octahedron can be readily developed, is therefore far more desirable than a twinned crystal, such as is shown in Fig. i, or an irregular crystal group which, as often as not, can be utilised only as bort.
The value of a diamond depends most of all, however, on the degree of its transparency, clearness, and purity, the colour it possesses, and its freedom from flaws. Of these qualities transparency and clearness stand first in importance, and the possession of these qualities in perfection renders a diamond extremely valuable.
Those faults, which impair the transparency and lustre of a stone, diminish its value very considerably. Large enclosures of black, brown, or of some other colour are frequently seen, as are also enclosures of “sand” and “ash”, and yellow spots technically known as “straw”. A fine surface polish over certain areas of a stone is often made impossible by the presence of white, grey, or brown “clouds” or by “icy flakes” of no definite colour, which are developed when the stone is allowed to become over-heated during the process of grinding. The existence of internal cracks following the direction of cleavage, and known as “feathers”, not only impairs the transparency of the stone, but also renders it liable to fracture during the process of grinding or when in use as an ornament. All these faults, even if insignificant in extent, become very obvious in the cut stone; numerous images of them are being reflected into the eye of the observer from the various facets of the stone. Should they be present in large numbers the stone is not worth cutting, but is regarded as bort.
With regard to the colour of diamonds, stones, which are perfectly colourless and water-clear are, as a rule, most highly prized, the so-called blue-white quality, which is more rare in stones from the Cape than in those from India or Brazil, being specially admired. Even a trace of colour, so small as to be indistinguishable to an unpractised eye, lowers the value of a stone very considerably, the diminution in value being still greater when the colour is more perceptible. Of coloured diamonds, those displaying tones of blue, grey, red, and yellow are preferred to those, which are coloured brown or black. A coloured diamond, which is lacking in transparency, is of very much less value than one of the same colour, which is clear and transparent.
Those diamonds which, in addition to perfect transparency and clearness, possess a pronounced and beautiful colour, are on account both of their rarity and beauty very highly esteemed, and always command a much higher price than the most perfect of colourless specimens. Among these so-called “fancy stones”, red, blue, green, and yellow specimens are included, the last-named, however, since the discovery of the Cape deposits, are by far the most common. Compared with colourless diamonds, coloured specimens exist in quite insignificant numbers. Diamonds showing different degrees of transparency and clearness and freedom from faults are usually classified as stones of the first, second, and third water, and are valued accordingly. Stones of the first water (1st quality) are perfectly colourless, transparent, and water-clear; they are free from any fault or blemish or tinge of colour and stand first in point of value. Colourless stones showing insignificant faults, or stones which are free from faults, but tinged with colour, are placed in the second division and referred to as stones of the second water, while stones of the third water display very obvious faults or a colour of undesirable depth. A further division of the stones of the latter description is sometimes made, and in this class are placed the smallest diamonds, which can be used as gems. It is by no means easy, however, in every case to place any given stone without hesitation in one or other of these three or four classes, and it may often be observed that a stone referred to as being of the second water by one jeweller will be placed in the first class by another. Generally speaking, it may be said that a brilliant of the second water has only about two-thirds of the value of a similar gem of the first water, while the values of two roses of the first and second qualities are in the ratio of four to three.
Taking the value of a brilliant of the first water as unity that of a similar brilliant of the second water will be 2/3, while the values of roses of the first and second water will be expressed by the fractions 4/5 and 3/5. It may be remarked here that it is almost impossible to classify rough stones in this way, since the qualities on which the classification depends are not sufficiently obvious until the stone has been cut.
It appears from the writings of Pliny, that among the ancients the diamond was regarded as the most costly of precious stones, and indeed of all personal possessions. Such, however, is not the case at the present time, for the price of a colourless diamond of good size is always exceeded by that of a ruby of the same size, and generally also by that of an emerald, or even of a blue sapphire if of special beauty. This, of course, does not apply to the few diamonds, which possess a fine colour in addition to their other beautiful qualities, the price of such stones being more or less prohibitive.
While the relative value of diamonds of different qualities changes but little, the absolute prices paid depend on a variety of conditions and are subject to considerable fluctuation. The earliest record in existence of the price of a diamond is that made by the Arabian Teifaschius, who, in the twelfth century, valued a 1-carat diamond at 2 dinars (about £6). In the year 1550, Benvenuto Cellini placed the value of a beautiful stone of the same weight at 100 golden scudi, a sum which is stated by Schrauf to be equivalent to 200 Austrian florins (£20), and by Boutan to 1,100 francs (£44). This latter value is abnormally high, and is probably based on an incorrect estimate of the value of the scudi. In 1609 Boetius de Boot gave the value of the carat-stone at 130 ducats (about £22), while the price mentioned in the anonymous work, The History of Jewels, published in London in 1672, is from 40 to 60 crowns (£8 to £12). This large fall in the value of the diamond is probably to be attributed to the effects of the Thirty Years War. According to Tavernier, the price of a carat-stone in 1676 was £8, and contemporary writers both in Holland and at Hamburg confirm this statement. The price of rough diamonds had sunk in 1733 to £1 per carat, but this fall was due to the panic, which followed the discovery of diamonds in Brazil. In the next year the price of the carat-stone had risen to £1 10s, at which it stood for several years subsequently. In 1750 the famous London jeweller, David Jeffries, the author of a Treatise on Diamonds and Pearls, records the value of a fine one-carat cut stone at £8, which is the same as the value given by Tavernier in 1676. In a work on precious stones, entitled Der aufrichtige Jubelier, published at Frankfurt-on-the-Main in 1772, the high price of 120 thalers (£18) is mentioned for a stone of the same description.
At the time of the French Revolution prices fell very considerably, and as far as can be ascertained from the valuation of the French crown jewels and from the prices fetched by the many less valuable stones which changed hands at this time, it would seem that in 1791 a one-carat cut stone would fetch no more on an average than £6. When more settled times came, however, and Napoleon’s luxurious court was established, the price again rose, and in 1832 £9 could be obtained for a one-carat brilliant, and rough stones of a quality suitable for cutting fetched 42s to 48s or even £3 per carat. Later on still, in the year 1859, rough stones of the same description were worth from £4 to £5 5s. per carat, while in 1860 and 1865 £13 to £18 was paid for a one-carat cut stone.
In the year 1869, shortly before the Cape diamonds came on the market, the following prices, according to Schrauf, were current: rough stones suitable for cutting, and similar to those which come in large parcels from the countries in which they are mined, cost £5 per carat; parcels of stones, the larger proportion of which could be used only as bort, made £1 to £2 per carat; while parcels containing nothing but bort were sold for 4s to 6s per carat. The prices recorded for cut stones show the importance, which was attached not only to the quality of a stone but also to the form and manner in which it had been cut.
A one-carat brilliant of the first water was worth £20 to £25, one of the second water £15, while one-carat roses of the first water were worth only £15 to £18; a brilliant of 1/2 carat would fetch £6, one of 1 carat £l2, and one of 1/10 carat £1; for small roses, of which 50 go to the carat, £15 per carat was paid; very small roses of about 1000 to the carat cost about 6d each. Only at most prosperous times, in the sixteenth and at the beginning of the seventeenth centuries, were such high prices paid as were current for diamonds in 1869. In the following table, compiled by L. Dieulafait, may be seen the prices in francs (25 francs = £1) which were paid for brilliants of 1 to 5 carats in the years 1606, 1750, 1865, and 1867. The prices current in the year 1878, which are given further on, are incorporated in this table in order to show the fall which took place in consequence of the discovery of the South African diamond-fields, and which followed a steady rise in the years 1867 to 1869.
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