The Process of Making Synthetic Diamonds
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Significance of Diamonds
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Diamonds, a special form of carbon created in an environment of extreme pressure and temperature, are some of the oldest minerals on Earth, but it has been in just the last century that humans have been able to replicate the natural process of creating the crystal. Diamonds are not only beautiful, but as the most durable substance known to humans, they are extremely useful for cutting, grinding, and other uses. Unfortunately, until people were able to synthesize diamonds, the difficulty of finding and processing the stones made them too costly for use in this manner.
Natural Diamond Production
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To make a diamond, nature needs carbon, heat, and pressure. In a diamond, carbon atoms arrange themselves in a tetrahedron, the strongest way that atoms can bond. At a depth of about 90 miles (150 kilometers) beneath the Earth's surface, the carbon atoms are heated to around 2,500 degrees F (1,300 degrees C), and subjected to pressure of 50,000 pounds per square inch (70,000 kg/cm2). Over time in this extreme environment, the carbon atoms form the tetrahedron bond which gives the diamond its strength. Through volcanic action, the stones eventually work their way to the crust of the planet where they are mined.
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Synthetic Diamond Production
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According to International Diamond Laboratories, a diamond-grading and reporting service, nearly 250,000 pounds of synthetic diamonds are produced around the world annually. Synthetic diamonds are indistinguishable from mined diamonds except under laboratory conditions, according to Apollo Diamonds, a firm that "grows" synthetic diamonds for semiconductor and other uses.
There are two ways to make a synthetic diamond. The older method, High Pressure-High Temperature Synthesis, essentially reproduces the conditions found in nature. At the center of a heavy press is a "core reaction cell," where the diamond will be "grown." Manufacturers place carbon and seeding material which will form the basis of the diamond in this cell. Next, a solvent of nickel or iron that acts as a transport material between the carbon and the seed is added. The use of the solvent allows the manufacturer to create a diamond at temperatures and pressures below those needed by nature. The HPHT system can create industrial grade diamond powder in just a few minutes, while a single gem-quality stone can take several days to produce. For the most part, the HPHT system is used to create industrial grade diamonds.The Chemical Vapor Deposition method of making diamonds was invented in 1952 by Union Carbide Corp. This method uses ultra-high temperature to create a plasma that breaks down atomic bonds and frees up the electrons. When diamond seeds -- about the size of a shirt button, according to the Apollo Diamond proprietary process -- are exposed to methane and hydrogen gasses at high temperature, carbon atoms from the methane precipitate, or "rain" onto the seed, creating a diamond, layer by layer. The CVD system allows for greater control of the growth, making it well-suited to creating gemstones.
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