mygemologists.com

Smaller brilliants are often not fully cut, that is, they do not possess the recognized number of facets, and these are known as single cut, half cut, or eight cut, in the trade. Such stones are often used in jewelry which contains a number of small stones, and their value is below that of the fully cut brilliant.

The girdle is rarely polished since it is almost entirely hidden when the stone is set. But if it is polished, it should be of knife edge thickness yet not extremely thin. Odd shapes lose in brilliancy, but an elongated culet to match the shape reduces this fault. There should be no culet in a modern cut stone, which should taper to a sharp point. A stone cut too “thin” or too “flat” gives a fish-eye effect and will have little value. A number of recently cut stones have this tendency of flatness, that is, too broad a table relative to the depth of the stone. A smaller number of facets than the normal, including a relatively small table, gives the stone a lumpy appearance, a fault quite common with old cut stones. These, which dealers class as “old cut,” “old mine cut” . or “Victorian cut,” realize appreciably less than the stones of modern cut. But if of good quality otherwise, and of some size, such stones are often worth re-cutting to the modern brilliant shape.

And now a few words on the judging and buying of gem stones, a feature which is generally neglected in works on gem-ology, although it is all important to many, and interesting to all. Everyone, even the trade buyer, wishes to get the best value for his money, so we will here try to point out what one must look for in the principal jewel stones, and how far faults affect prices.
With stones, the more one spends, the better relative value one should obtain. If one can afford it, or if one is buying with a view to investment or subsequent resale, it cannot be too emphatically advised that the quality of the stone is far more important than the size. A good quality stone is always saleable, and a fine and large precious stone appreciates in value. First quality diamonds, emeralds, and rubies of size are rare, and they are eagerly sought after. A readily portable fortune, which can be realized in any civilized country, can be invested in such stones.

Most of the jewel stones which lie outside the range of the precious are not of great commercial value, but again the fine and large specimens are the more easily realized for money, if necessary. Comparison of different qualities in gem stones should be made; the stocks of first class jewelers should be studied, and visits to museums or collections which contain noteworthy specimens will be of assistance in gathering information. Every capital, and many large provincial cities, can show excellent stocks of gem stones in normal times. One should buy from reliable shops or experienced dealers, and not on trips to the East in various ports of call,  unless one has reason to be confident.  Many a synthetic stone, and even pastes, have brought much money to dealers in Cairo, Colombo, Singapore, and other ports, and also disappointment to the purchasers.

Alluvial deposits are the easiest to work for the individual prospector. In addition to gem stones, gold, platinum, tinstone, and osmiridium are among the metals of value which are found in such deposits. Very little capital is required to work them. Alluvial drifts, river beds and creeks should be carefully examined. A pick, shovel, a tin dish for panning, and a large knife is necessary. Pits in beaches and gravels along the course of the stream should be dug until the rock is reached, and the material raised should be panned. The heavier stones and material will remain.

The determination of minerals is made by tests or observations which involve the following: crystalline structure, cleavage, luster, color, hardness, streak, malleability, smell, taste, specific gravity, blow-pipe characteristics, dichroism, and refractive index. With gem stones, some of these tests would not apply; indeed, not all of these tests would be practical or necessary for any one stone or metal. In previous chapters, we have dealt with most of these properties of minerals, and an idea of the conclusions reached by these tests will be apparent to the reader.

The chemical test of the blow-pipe, most important with metals, is not so important to the gemologist. The whole subject is, of course, enormous, and a variety of larger and more specialized works which devote themselves to these specific branches of mineralogy may be consulted. Here, we have given just a brief sketch of prospecting and may have possibly whetted, or diminished, the appetite of the reader.

If one breathes on a diamond so that its dispersion is temporarily dimmed, a quick examination may help to detect spots or faults within the stone. As the cloud vanishes, black spots are more easily seen since they are not masked by refraction of light from the facets. The stone should be examined from different angles as the color may vary in different directions, or minute cracks may be more apparent in certain positions. A small crack may sometimes show a chromatic effect at certain angles only. A good lens is essential here and, of course, good eyesight.

It should be remembered that masses of stones appear deeper in color than single stones (more especially zircons and aquamarines). Light reflected from a mount may affect the color. For instance, yellow gold sometimes tends to impart its tinge on to a white stone, so all gems should be examined unmounted, if this is possible. With diamonds, the so-called fancy colored stones are scarce, yet they have no regular market value. They are often difficult to sell. Yet very few stones are really white. There is a fairly generally accepted name for each shade of color with diamonds, such as Jagers, rivers, Capes, all of which are used by experienced dealers in the trade, but these names do not, nevertheless, change the quality of a stone.

In many districts, both precious stones and metals occur, so the miner should have a wide knowledge in order to make the best of his finds. He may commence by seeking black opal and finish by finding gold. Or he may be mining for emeralds and find diamonds. Prospectors are usually of a restless type; even if they are successful and strike lucky, news of a new field will cause them to desert their finds and hurry off to the the newly opened up area which, of course, may well prove worthless. Prospecting becomes a fever, and one seldom gives it up willingly. The free and easy life, the change of scene, the chance of making a fortune in one day, and perhaps even the intense physical hardships, cast a glamor over the life which is often irresistible.

The ease with which gold is recognized, its high international value and easy disposal, makes it the object of many a prospector, but diamonds, sapphires, emeralds, rubies, opals, and pearls all find easy buyers if the stones are of gem quality. There will be no difficulty in disposing of any of these minerals in the rough to local buyers, while there are many purchasers, dealers, lapidaries, and merchants in London, New York, Paris, and in other cities. It is more difficult to know what one should obtain for gem stones than for precious metals; the miner is often unfamiliar with current market values. Experience soon teaches.

Some knowledge regarding the methods of working and determination whether the mineral or metal is present, in sufficient quantity to make the deposit payable must be obtained. This more directly concerns the miner of gold and other metals, and he will have to sample the ore by panning tests or assay methods. If large scale mining is intended, many other points have to be considered. Available water power for electrical, mechanical, and metallurgical installations, the presence of fuel, labor, timber, rail or road communications, and other factors are of utmost importance.

We have indicated in a previous chapter the approximate values of many different varieties of gem stones, and such values will have more meaning if one is able to judge qualities, which involves the recognition of faults and the appreciation of the merits of a given specimen. It is important to remember what is considered the best color and quality of the various varieties. Diamond is probably the most popular gem stone and the one most widely bought by the public, so we will add some further remarks on what constitutes a good stone.

In diamonds, we look for absence of color, since all color is due to minute impurities. Pure white is therefore considered perfection, but in reality, such stones are rare. The tints of color which one almost always sees are usually yellow or brown, and they are faint, passing to white by very fine graduations. Practice in detecting such different shades is necessary; stones should be viewed in a good north light, unobstructed, with no colored surface near so that light is reflected on to the stone. The morning is the best time to look at stones to see their true color, and dull and dark days should be avoided. Artificial light may give a false impression. It is almost impossible to carry color in one’s mind for the purpose of comparison, but judging in the same surroundings helps. This is one reason why stone merchants always like to buy in their own offices. But these ideal conditions are seldom present, and one should learn to judge stones in less favorable circumstances.

Although the mining engineer may be equipped with better tools today and transport may be much more speedy and convenient than in former years, there may be other disadvantages in this age of limited freedom. He will, most likely, be hampered by laws and restrictions, and he may come in contact with state ownership and control, or private rights already assigned to large syndicates. If employed by a large company, he will no doubt be provided with all the required information and equipment. We are concerned with the roving prospector with limited scientific knowledge who often possesses local data and an abundance of optimism and spirit. He usually knows little about the geological age of rocks, but he knows by sight if there is a likelihood of minerals being present by the nature of the country.

The geological structure of the district may, in many instances, have already been thoroughly examined by government survey, and reports may then be obtained and studied. As is well known, certain minerals are generally associated with definite rocks, although this is no sure guide that such minerals are present even if those rocks are found. A new arrival in a district cannot hope to be successful unless he first studies the local government reports or those of experienced and reliable natives.

Certain tools are necessary; amongst these will be a blowpipe and its accessories for easy identification of minerals, a compass, a pick, a file, and the usual impedimenta necessary for traveling, eating, and sleeping. A week’s residence in a mining camp will give the prospector much more practical knowledge than any book could hope to give him. He may work on a claim, or go into partnership with another miner for experience before prospecting on his own account. But his theoretical knowledge will always stand him in good stead. A large reserve of optimism is necessary, and good luck is the best tool of all although it is one which, unfortunately, cannot be bought.

We will say only a few words about prospecting for precious stones as it is a subject in which practical experience counts for almost everything. As the reader will realize, the value of gem stones already recovered from the earth, the sea, and river beds must amount to hundreds of millions of dollars or pounds, but it is quite certain that far more lies buried and only awaits the hand of man to be brought to light. It is true that one must now often dig deeper than those who prospected some hundreds of years ago, but with modern appliances and our extended knowledge of the earth, this presents less difficulty, in theory.

Vast fields in every continent outside Europe still await the pioneer, and apart from syndicates and companies, there are many adventurous individuals who are reaping rich rewards for their labors. But the life of a prospecting miner is not an easy one. Living conditions are generally primitive; he may be obliged to work in isolated districts, in desert or mountainous country. Climatic conditions may be severe, and heat and hunger will try his patience and determination, even if he be lucky in his work. Yet in Australia, South Africa, and South America, and in the tropical seas, there are many men who endure such hardships for the sake of adventure and gain.

When one reads of the experiences of some of the prospectors of our times, such as Wollaston, who sought opals and other precious stones in Australia ( Opal, the Gem of the Never Never), and Berge, who dived for pearls (Pearl Diver), it will be realized that, to be an individual prospector, it is necessary to be born with at least an adventurous spirit and a stout constitution.
To the prospector, an ounce of experience is worth a ton of theoretical knowledge. But he should get as much information as possible concerning the geology of the country which it is proposed to prospect, and this would include the general mode of occurrence of the minerals in view, together with the rocks and other minerals with which they are usually associated. One must know how to distinguish between minerals in the rough by fairly easy, but certain and quick, methods. Then there is the question of local mining laws which must be respected, the ultimate disposal of minerals found, and the supply of food, shelter, and tools. Various licences for prospecting and exploitation are generally required; mining leases, concessions, and exclusive permission to explore specified areas have to be obtained and paid for according to the laws of the country.

“Silk” is a fault, as are also fissures and cracks. They are by no means uncommon. Facets should be examined for nicks and cracks; they are often seen in old stones. Surface scratches due to wear can be polished out, and sometimes old stones with irregular facets can be recut to advantage. Proportion in width and depth should be good. Blackish stones, generally of Australian origin, are not worth much. The bright but pale stones are of more value, but these do not approach the prices reached by Cashmere, Burma, or Siam stones. Most of the fine Cashmere stones are now to be found only in old jewelry.

Sizes from three to five carats are ideal for ring stones. Large stones, up to fifty carats, are sometimes seen, but these are exceptions, particularly if they are of fine quality, and they can realize $560 (£200) a carat. The medium size stones are worth about $56 (£20) to $210 (£75) a carat if of good quality and color. Those of one to three carats obtain about $56 (£20) to $112 (£40) a carat, if fine.

Good imitations of amethyst have been made in paste, and some of these may be found in old jewelry. It is worth while applying a simple test, such as that of hardness, if there is any doubt.

Kunzite, to be of value, should be flawless and of a decidedly pinkish shade. Small specimens are of little value since their color is almost always pale. Sphene is not often seen in jewelry; it is rather soft, and cut stones soon become scratched in wear. The better specimens are very bright, and they can realize $140 (£50) a carat or more.

Of the many other uncommon jewel stones which we have mentioned, there is not much to add here, except to say that their occurrence in jewelry is rare and comparatively isolated. A jeweler may be in business for many years before he encounters scapolite, or phenakite, or epidote in a mounted article; such stones are for those who take more than an average interest in the precious minerals, the collectors and the connoisseurs. Moreover, such stones have no precise market value, any more than have the single specimens of “new” minerals which are found from time to time. We are, of course, considering jewel stones from a purely commercial point of view in this chapter, but there are many to whom this angle is of first consideration and importance. The scientist is not often concerned with supply, demand, and price fluctuations.