celebrating 27 years of excellence!
Diamond, one of the world's most important mineral resources,
is pure, natural carbon with the atoms organized in a close-packed cubic
arrangement that gives the stones their hardness. The external forms of
natural diamond crystals (isometric system) shows the same symmetry. The
most common crystal form is the octahedron, which looks like two four-sided
pyramids placed base to base.
Because diamond is so much harder than any other natural or artificial substance
known, it is ideal for both gem and industrial purposes. Special optical
properties guarantee its preeminence among gems. First, its high refractive
index (2.417), or light-bending ability, enables it to throw back almost
all the light that enters a well-cut gem. This gives rise to the gem's brilliant,
or adamantine, luster. Second, it exhibits strong dispersion (0.058), or
the ability to separate the various colors of the spectrum. This causes
the gem to throw back the bright flashes of separated colors ("fire")
for which it is particularly noted.
GEMSTONES
Fewer than 20 percent of the diamonds mined each year are suitable for use
as gems. Most are sold at monthly "sights" through the Diamond
Trading Company in London. At a "sight" the buyer is presented
with a parcel of uncut stones to examine; the buyer must either purchase
or reject the entire package without choosing among the various stones.
The stones are finished in various kinds of cuts, or "makes."
The best proportioned ones throw back the most light. No universal standards
have been adopted for "make," but the American Standard Brilliant
Cut or "Ideal Cut" is the closest to ideal proportions. Finished
stones are graded according to quality and then marketed. Various classification
systems--based on color, clarity (freedom from flaws and inclusions), cut,
and carat weight--are used to determine quality and, thereby, the market
value of gem diamonds.
The largest single rough diamond ever found, the Cullinan diamond, found
in 1905 in South Africa, weighed 3,106 carats. Several other large stones
have been found, including the Excelsior (1893), weighing 995.2 carats and
also from South Africa, and the Star of Sierra Leone (1972), weighing 969.8
carats and from Sierra Leone. Several fine gems were cut from the Cullinan,
including the world's largest, the Star of Africa (530.2 carats), now in
the royal scepter of the British crown jewels.
The Hope diamond, an infamous natural deep-blue diamond of 44.5 carats,
most likely came originally from India. It is now in the gem collection
of the Smithsonian Institution in Washington, D.C. It demonstrates the beauty
of "fancy," or highly colored diamonds, which are also found in
shades of yellow, pink, blue, and other colors.
INDUSTRIAL USES
Industry uses most uncut diamonds. Diamond-studded rotary bits are used to drill oil wells and bore tunnels in solid rock. Much low-grade diamond is crushed to dust, sorted by grain size through special sieves, and used as abrasive powder. Depending on the kind of abrasion or grinding needed, the powder is either sintered into metal disks, formed in carbide grinding wheels, pressed into metal, or mixed in an oil paste. The powder is also used to cut and polish gems. Diamond-tipped glass cutters, glass-etching pencils, and other similar tools find widespread use. Very thin wire is formed by pulling thick wire through a graduated series of diamonds with tiny holes drilled through them. diamonds for industrial purposes have been synthesized since the 1950s using high-temperature, high-pressure techniques, and since the 1960s using shock-wave techniques. (Gem-quality diamonds can also be synthesized, but the process is costly.)
Technological uses for diamonds were expanded the late 1980s by the development
of methods for depositing diamond coatings on surfaces. Such uses include
the coating of integrated circuits as a whole instead of having to coat
the components of the circuits individually. The coatings may also be used
in prosthetic devices and biosensors.
MINING AND PRODUCTION
diamonds occur in two general types of deposits: volcanic pipes through which molten rock--Kimberlite, now cooled and hardened--rose up from deep within the Earth, and alluvial, or placer, deposits, which were formed by the erosion of diamond pipes over millions of years.
The earliest productive mines were in the Golconda region of India, particularly along the Kristna River. After 1725 this mining district was gradually eclipsed in importance by the diamond deposits of Brazil. diamonds were first mined there along the Jequitinhonha River, in the Diamantina area of the state of Minas Gerais.
In 1867 a 21-carat stone was discovered on the banks of the Orange River
near Hopetown, South Africa. A great diamond rush started, and new deposits
were discovered that were more productive than any the world had ever known.
Another major diamond resource was developed in the 1950s in the Yakutia
region of the Soviet Union. By the 1980s the Yakutia and South African regions
and the country of Zaire dominated the world's diamond market. The mineral
has also been found in smaller amounts in numerous other places. In the
United States the leading producers include Arizona, Nevada, and Montana,
although the largest gemstones have been found in an eroded volcanic pipe
in Pike County, Ark.
For many years, microscopic diamonds have occasionally been noted in meteorites;
they were attributed to high-speed collisions in space or with the Earth.
In 1987, however, following the discovery of many more such diamonds, the
theory was developed that they are the product of ancient supernova explosions
of giant stars.
Bibliography: Bachman, P. K., and Messier, Russell, "Emerging Technology of Diamond Thin Films," Chemical & Engineering News, May 15, 1989; Beatty, J. Kelly, "Stardust on Earth," Sky and Telescope, June 1987; Boyd, F.R., and Meyer, H. O., eds., Kimberlites, Diatremes, and diamonds (1979); Davies, Gordon, Diamond (1984); Gemological Institute of America, The Diamond Dictionary, 2d ed. (1977); Orlov, Y. L., The Mineralogy of the Diamond (1977).
Thomas Michaels Designers, a third generation of contemporary American award winning diamond jewelry design.
Northern New England's premier designers and manufacturers of fine handmade contemporary and classical diamond jewelry as well as respected fine jewelry retailers. We are special order diamond jewelry design experts and renowned suppliers of exceptional white diamonds and exotic natural colored diamonds and fine colored gemstones.
Known as designers extraordiniare and international suppliers of exquisite diamonds.