Natural Diamonds.
Most natural diamonds are formed at high temperatures (900oC – 1300oC) and pressures (4.5GPa – 6GPa) deep inside the Earth’s mantle over periods of 1 billion to 3.3 billion years. Carbon used in this process are obtained from carbon-containing minerals present in the mantle. These diamonds are brought up to the Earth’s surface by volcanic eruptions.
Some diamonds are formed at the site of a meteorite strike, which met the conditions of high temperature and pressure; and containing carbon-bearing mineral. Sometimes, interstellar meteorites, that contain diamonds, deposit these precious stones through impact on Earth.
Synthetic Diamonds.
Synthetic diamonds are formed by either high-pressure high-temperature (HPHT) or chemical vapour deposition (CVD) crystal formation methods. HPHT method involves conversion of carbon, like graphite, at high temperature and pressure into diamond. On the other hand, CVD method involves mixing varying amounts of carbon-containing gases in a chamber and energizing them, for instance by means of a laser beam, to form diamonds. The growth diamond by CVD method typically occurs at pressure ranges of 1kPa to 27kPa.
Diamond Simulants.
Diamond simulants are not actual diamonds. They are gemstones that resemble diamonds in appearance and many other characteristics. Cubic Zirconia and Silicon Carbide are examples of diamond simulants.
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