In spite of some uncertainty in extrapolating the HPHT data to natural conditions in the SCLM, it appears that higher temperatures toward the base of the lithosphere could lead to reduction or elimination of the brown color within thousands of years. Crystals of brown diamond stored at or below about 1000☌ should maintain their color for 10 8 years or more. The time necessary to remove the brown color in the SCLM is significant on a geological time-scale. A critical component of this calculation is the activation energy for the breakup of vacancy clusters. As there has been speculation that a similar removal of color should occur continuously at depth in the subcontinental lithospheric mantle (SCLM), the effect of temperature on the time required to eliminate the brown color in diamond has been calculated from published data. A brief treatment in a high-pressure – high-temperature (HPHT) vessel at 1800–2700☌ can remove this color. ![]() ![]() ![]() The common brown color in natural diamond is likely caused by vacancy clusters, produced by plastic deformation of the crystal structure.
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