The HPHT process is very costly, given the energy and equipment required, and produces diamonds with mainly yellowish or brownish yellow colors. ![]() The HPHT method, first used to successfully grow diamonds by General Electric in 1954, essentially mimics the natural process - carbon is crystallized as diamond through intense heat and pressure deep within the Earth. This causes the carbon atoms to accumulate on a substrate (a small platform containing a flat diamond seed crystal, usually an HPHT synthetic), similar to the way snowflakes accumulate in a snowfall. The process involves introducing a gas, such as methane, into a vacuum chamber, then activating and breaking down the molecules of the gas with microwaves. They are also vastly different from the High Pressure, High Temperature (HPHT) synthetics that have been manufactured since the mid-1950s.ĬVD synthetic diamonds began appearing in the gem diamond market about a decade ago. CVD-processed stones are much different from the natural diamonds produced by geologic forces. Image © GIA.Ĭolorless synthetic diamonds produced by Chemical Vapor Deposition (CVD) are becoming more common in the market. sample on the right was graded J color and VVS2 clarity. ![]() round brilliant on the left was graded F color and VVS2 clarity the 0.83 ct. Manage Your GIA Alumni Association™ MembershipĬVD synthetic diamonds produced by Gemesis. Comprehensive CAD/CAM For Jewelry Certificate
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