High pressure/high temperature production of colored diamonds

摘要

The present invention is directed to a method for treating discoloured natural diamond, especially Type IIa diamond and Type IaA/B diamond with nitrogen as predominantly B centres, for improving its color. The method includes preblocking and preshaping a discoloured natural diamond to prevent its breakage in a high pressure/high temperature (HP/HT) press, placing said discoloured natural diamond in a pressure transmitting medium which is consolidated into a pill. Next, the pill is placed into a HP/HT press at elevated pressure and elevated temperature within the graphite-stable or diamond-stable range of the carbon phase diagram for a time sufficient to improve the color of said diamond. Finally, the diamond is recovered from said press. Colorless and fancy colored diamonds can be made by this method.