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.

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.

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.

Abstract: A long life mercury vapor discharge lamp is provided. The lamp has a ultraviolet-reflective barrier layer, a rare earth triphosphor layer coated on the barrier layer, and a fill gas of mercury vapor and argon. Most preferably, the barrier layer has a coating weight about 2.6, mg/cm2, the phosphor layer has a coating weight of about comprising a light-transmissive glass envelope having an inner surface, means for providing a discharge, an ultraviolet reflecting barrier layer comprising alumina particles coated adjacent said inner surface of said glass envelope, a phosphor layer coated adjacent said barrier layer, and a discharge-sustaining fill gas of mercury vapor and argon sealed inside said envelope, said fill gas having a pressure of 2.9-5 torr at 25° C., said phosphor layer having a coating weight of 2-3.5 mg/cm2.

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.

Abstract: A long life mercury vapor discharge lamp is provided. The lamp has a ultraviolet-reflective barrier layer, a rare earth triphosphor layer coated on the barrier layer, and a fill gas of mercury vapor and argon. Most preferably, the barrier layer has a coating weight about 2.6, mg/cm2, the phosphor layer has a coating weight of about comprising a light-transmissive glass envelope having an inner surface, means for providing a discharge, an ultraviolet reflecting barrier layer comprising alumina particles coated adjacent said inner surface of said glass envelope, a phosphor layer coated adjacent said barrier layer, and a discharge-sustaining fill gas of mercury vapor and argon sealed inside said envelope, said fill gas having a pressure of 2.9-5 torr at 25° C., said phosphor layer having a coating weight of 2-3.5 mg/cm2.

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 placing a discolored natural diamond in pressure transmitting medium powder 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 within the 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 diamond can be made by this method.

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 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 within the graphite 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 diamond can be made by this method.