Gemstone Diamonds

Ward, F. 1998 Diamonds. Bethesda, MD, USA Gem Book Publishers. A compact book with many photographs telling the history of diamond gemstones. 

Zirconium silicate (ZrSiO ) is one form of the mineral whose crystals when polished are known as cubic zircons, which resemble diamond gemstones. 

So-called "memorial" diamonds are a recent trend in the jewelry industry. They are diamonds made—quite literally—from human remains. A number of companies now offer to cremate the body of a loved one or pet and use the carbon contained in the body to create a diamond gemstone. The new diamonds, forms of pure carbon, are marketed as the ultimate, wearable keepsake of the dearly departed. 

As mentioned above, diamond gemstones stiii remain the major use of diamond in monetary terms in a market tightiy controiied by a woridwide cartei dominated by the de Beers organization of South Africa. ] Some maintain that the cartei keeps the cost of gemstones at an artificiaiiy high ievei and that the supply is abundant. Control of the price of industrial diamond is not quite as obvious. 

Diamond simulants are usually included under synthetics, even though not all of these have been synthetic gemstone materials, such as the garnets. 

Diamond is supreme among natural gemstones ia H, RI, and DISP. Table 3 shows the steady improvement ia the sequence of diamond imitations, the aim being to produce a colorless, adequately hard material having closely matching optical properties. The iatroduction of synthetic cubic 2irconia ia 1976 brought about a sufficiently close match. 

Table 3. Properties of Diamond and Synthetic Gemstone Materials ...

Several gemstone species occur in various colors, depending on the presence of impurities or irradiation-induced color centers. Examples are the beryl, comndum, and quart2 families. Quart2 has poor optical properties (RI = 1.55, DISP = 0.013), but becomes of gemological interest when it exhibits attractive colors. Any material can have its color modified by the addition of various impurities synthetic mby, sapphires, and spinel are produced commercially in over 100 colors (2). Synthetic cubic 2irconia has been made in essentially all colors of the spectmm (11), but only the colorless diamond imitation is produced commercially in any quantity. 

With the exception of diamond coloring and the turning of topa2 blue, the source of the irradiation is immaterial. Gamma rays are the preferred source because of uniformity of coloration and the absence of heating and induced radioactivity. The most commonly seen gemstones enhanced by irradiation are summari2ed in Table 4. 

Optical Properties. The high refractive index (2.42 at 589.3 nm) and dispersion (0.044) are the basis for the brilliance and fire of a properly cut gemstone. The optical transmission out to 10.6 p.m for Type Ila diamonds makes possible windows for CO2 lasers and for devices such as were in the... 

Diamond is an important commodity as a gemstone and as an industrial material and there are several excellent monographs on the science and technology of this material [3-5]. Diamond is most frequently found in a cubic form in which each carbon atom is linked to fom other carbon atoms by sp ct bonds in a strain-free tetrahedral array. Fig. 2A. The crystal stmcture is zinc blende type and the C-C bond length is 154 pm. Diamond also exists in an hexagonal form (Lonsdaleite) with a wurtzite crystal structure and a C-C bond length of 152 pm. The crystal density of both types of diamond is 3.52 g-cm. ... 

Crystals are familiar to everyone, eommon examples being salt and sugar. Less eommon but more alluring are diamonds and other gemstones. More prosaie are the innumerable erystals manufaetured in the bulk, fine ehemieal and pharmaeeutieal industries, in both primary produets, seeondary formulations and their intermediates. As illustrated by the erystal produets in Table 1.1, their range is immense and ineludes some highly sophistieated materials. Similarly, worldwide produetion rates and value are ever inereasing. 

Natural diamonds are divided into three categories. First are the carbonate or black diamonds. These are the hardest and most expensive diamonds. They are used primarily as gage reinforcement at the shockpoint. Second are the West African diamonds. These are used in abrasive formations and usually are of gemstone quality. About 80% of the West African diamonds are pointed in shape and, therefore, 20% are the desirable spherical shape. Third are the Congo or coated diamonds. These are the most common category. Over 98% of these diamonds are spherical by nature. They are extremely effective in soft... 

Apart from their appeal as gemstones, diamonds possess a remarkable... 

Diamond Carbon Colorless 3.5 10 Crystalline Gemstone, abrasive, flux, and lapidary... 

Cutting, grinding, and shaping stone, and in particular burnishing and polishing the surface of stone as well as metals, requires the use of abrasive materials that are harder than the solids to be cut, ground, burnished, or polished. Sapphire and ruby, two very hard gemstones, for example, can be cut or polished only with the assistance of diamond powder, an abrasive that is harder than sapphire or ruby. Diamond is the hardest material... 

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