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Turquoises should be blue to be of any value. Bluish green, green, and a dull, dirty green are all inferior qualities. The inclusion of matrix (black or brown) and other foreign matter which is often seen on the surface of a stone is also a detraction. Really fine blue turquoises of size are scarce, yet $2.80 (20/-) a carat would be a high price for such stones. Very good imitations of this stone are made from blue glass, blue china, and blue enamel.

Good quality lapis lazuli is not uncommon, but it is a stone which is not much used in jewelry. One should look for a deep blue, unspoiled by white or gray streaks and patches. The included iron pyrites as a few specks is no great deterrent to appearance or value. There is little else which can be confused with lapis lazuli. Glass, suitably colored is the best imitation, the commercial Swiss lapis being obviously different to the naked eye.

Fine jade (jadeite) is very scarce, although inferior quality pieces abound. These latter are of little value, as is also the greenstone (New Zealand) variety. Fine jade is a deep green, full of life, and almost like an emerald except that it is translucent and not transparent. It should be free from blemishes, which are usually of a white or gray character, and it should contain no cracks. The colored varieties of jadeite, the pinks, mauves, reds, and browns, are generally of a pale shade, and these are not of great value. Fine pieces of jade realize high prices, although their market is a restricted one. Individual collectors and connoisseurs are the chief buyers of such stones.

Although many people seem to expect to see a flawless white stone, it may be said that flaws of some kind are almost always present in diamonds, despite the efforts of the lapidary to hide them and the protestations of the salesman to minimize them. The most common faults are small black spots, and these may be present in otherwise good quality stones. If above the girdle, they are more obvious than if below the girdle, but in all instances, value is lessened thereby. Spotted stones are called pique goods in the trade.
Cracks are frequently present, generally very small internal flaws resembling a short length of hair. Light is reflected from such broken surfaces, and these flaws are thus more easily seen in certain directions. Minute cavities or bubbles, which may be empty or filled with carbonic acid, are also not uncommon, but all these faults will not be easily seen except in bad quality stones. Careful examination in various directions is necessary, using forceps or tweezers, not the hands, to hold the stone.

Then we have defects in cutting and polishing which decrease the value of stones. These defects may have a purpose, such as retaining more weight to the detriment of proper shape, or they may be due to lack of skill on the part of the lapidary. Small, unpolished surfaces may be present, or there may be nicks or chips, these often being present in the girdle. Such defects may be minimized if the stone is set in a clever mount. Chips may be due to careless cutting or, in old stones, unskilful unsetting from a piece of mounted jewelry. The careless stocking of loose stones may show in small surface marks, these being caused by the stones rubbing against each other. This holds for all varieties of gem stones. Surface lines left from the polishing wheels are also sometimes seen on the facets.
In addition to these defects we have, of course, the defects of color, and especially a milky hue which clouds some specimens. This is due to irregularity of composition, and it is generally obvious to the naked eye. Each and all of these faults lessen the value of the specimen, but the degree of depreciation is one of current market values and cannot be judged except by those who handle stones daily.
In well cut modern stones, the proportions and facet angles should be approximately those already noted, and all facets in the same set should be alike in size and shape. Therefore, each large facet of the stone should be patiently examined, both from the back and the front. But it should be realized that very few stones are perfectly flawless. In practice, small differences in shape are often not seen, weight being retained to the detriment of good proportion.

We will conclude with a list of stones which are to be found in modern jewelry. All other stones not mentioned in this list are mainly of academic interest only.
Diamond.
Sapphire (mainly blue), and star stones. Green and purple are uncommon, but white used in cheaper forms of jewelry.
Emerald.
Ruby  (star ruby uncommon).
Pearl  (real and cultured).
Opal  (all varieties, the least used being fire opal).
Aquamarine.
Tourmaline  (mainly green and pink).
Spinel (all colors, but mainly red and blue; not greatly used).
Topaz   (mainly yellow, some pink).
Zircon (blue, white, some yellow and brown).
Chrysoberyl   (all fairly uncommon).
Garnet (mainly pyrope and almandine; hessonites uncommon, demantoid rare).
Kunzite  (rare in Europe).
Sphene   (rare; usually brownish yellow in color).
Peridot (usually green).
Beryl (mainly pale and intermediate shades).
Quartz (most varieties are used, but especially amethyst, carnelian, and rock crystal).
Turquoise.
Lapis lazuli.
Jade (jadeite is more common than nephrite).
Moonstone.
Amazonite.
Labradorite.
Malachite.
Fluorspar  (mainly Blue John in England).
Steatite (soapstone).
Also amber, coral, jet, ivory, bone.

When considering rubies and sapphires, including the star stones, the prevalence of synthetics should be borne in mind, and large and apparently perfect stones should be very critically examined. Do not assume that all the rubies or sapphires in a piece of jewelry which contains many stones are real. Some may have been replaced by pastes or synthetics, and new pieces of jewelry containing diamonds and synthetic colored stones are not uncommon. Star stones are also simulated by star quartz suitably backed, especially in larger sizes. Stones in closed settings should not be bought if the amount involved is large, unless one is prepared to gamble. They may be doublets or synthetics, despite their apparent age or history. Rubies are relatively heavier than diamonds, but as they are often cut in forms other than the brilliant, their weights should be estimated with caution. Actual weighing by a balance is the surest means.

With emeralds, depth of color with brilliancy and the absence of flaws are the chief features to look for. A deep green, showing brilliancy, is the best, but stones are too often pale. Sometimes this is caused by the specimen being cut too shallow for want of sufficient material. Other stones are too dark, which also detracts from their value. Surface marks due to wear may be eliminated by careful polishing, but the lapidary cannot eradicate internal flaws. Such internal fissures and spots are most common in emeralds; in fact, a flawless stone is an exception, and some of the better specimens which reach $1,400 (£500) a carat and more are not entirely free of small flaws. A really flawless emerald of three carats or more might fetch a very high price  (they have sold for
$5,600 (£2,000) a carat), so it is as well to examine such stones very carefully when they appear. But the color must be a brilliant velvety deep green to make the stone of first grade.

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.