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  • September 30, 2021

High Pressure, High Temperature (HPHT) Diamonds

Designed in the 1950s, High-Pressure, High-Temperature (HPHT) is a diamond treatment in which both high pressure and high temperature is applied to natural diamonds that are not fully crystallized when released from fiery, erupting volcanoes in order to improve their color. Nearly all “white” diamonds contain some degree of brown or yellow color.

The HPHT Process

The HPHT technique is a carefully controlled scientific procedure that can be applied to diamonds that contain nitrogen (Type I), which turns the diamond yellow, or to diamonds that are nearly free from nitrogen (Type II), which makes the stone colorless. This process is used to finish what nature started by applying the same atmospheric pressure that a diamond receives underground at temperatures up to 3,700 degrees F.

Replicating these conditions will bring a diamond to its complete, “mature” state. First, a highly trained gemologist positions the diamond into a containment cube surrounded by heating mechanisms. The cube is then placed in a press to apply the extreme pressure of 70,000 atmospheres, resulting in the stone’s most colorless and desirable state. The HPHT maturation process is permanent. Even though heat and pressure is applied to improve color, it is important to note that these stones are 100% natural diamonds.

HPHT can only be used on high-clarity diamonds because the extreme pressure and temperature can cause diamonds with fractures or inclusions to become frosted or even explode during the process, rendering the stone useless.

HPHT diamonds are genuine, natural diamonds that were formed inside the earth and erupted through volcanic activity. Undergoing the extreme pressure and temperatures applied during the mechanical process further enhance the stone’s color and desirability. Gary J. Long Jewelers is proud to carry Bellataire HPHT diamonds, whose process provides the highest pressures used in HPHT processing, resulting in virtually no surface burning and far less breakage to lower clarity diamonds. Further, Bellataire has earned the highest safety rating among HPHT Service Providers. Visit us today for more information and to see our collection in our newly remodeled showroom!