Abstract: The present invention is directed to a method for changing the color of colored natural diamonds. The method includes placing a discolored natural diamond in a pressure-transmitting medium which is consolidated into a pill. Next, the pill is placed into a high pressure/high temperature (HP/HT) press at elevated pressure and elevated temperature for a time sufficient to improve the color of the diamond. The diamond may be exposed at elevated-pressure and elevated-temperature conditions within the graphite-stable region of the carbon-phase diagram—without significant graphitization of the diamond, or above the diamond-graphite equilibrium and within the diamond-stable region of the carbon-phase diagram. Finally, the diamond is recovered from said press. Colorless Type Ia and Type II diamonds may be made by this method.
Type:
Grant
Filed:
December 15, 2003
Date of Patent:
January 29, 2008
Assignee:
Bellataire International, LLC
Inventors:
Suresh Shankarappa Vagarali, Steven William Webb, William Edwin Jackson, William Frank Banholzer, Thomas Richard Anthony, George Rene Kaplan
Abstract: The present invention is directed to a method for treating discolored natural diamond, especially Type IIa diamond and Type IaA/B diamond with nitrogen as predominantly B centers, for improving its color. The method includes preblocking and preshaping a discolored natural diamond to prevent its breakage in a high pressure/high temperature (HP/HT) press, placing said discolored 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.
Type:
Grant
Filed:
August 8, 2001
Date of Patent:
July 10, 2007
Assignee:
Bellataire International, LLC
Inventors:
Thomas R. Anthony, Yavuz Kadioglu, Suresh S. Vagarali, Steven W. Webb, William E. Jackson, William F. Banholzer, John K. Casey, Alan C. Smith