Diamond Education

HPHT and CVD: How Laboratory-Grown Diamonds Are Made

HPHT and CVD describe two methods used to manufacture diamond. They explain a part of the stone's growth history, not a complete quality assessment.

Understanding the terms helps you read product descriptions without turning a growth-method label into a shortcut for selecting a stone.

High Pressure, High Temperature

HPHT growth uses high pressure and high temperature in specialized equipment. A carbon source and diamond seed are involved in a process that allows diamond to grow under controlled conditions.

The resulting crystal is then fashioned into the desired finished form. HPHT also appears in the context of some diamond treatments, so the word should be interpreted according to the statement in which it is used.

Chemical Vapor Deposition

CVD growth uses a carbon-containing gas environment and a diamond substrate. Under controlled conditions, carbon is deposited as diamond growth develops.

Growth method and any later treatment are separate subjects. A description of how a diamond was grown should not be treated as a complete statement about everything that happened afterward.

What a growth method does not tell you

Knowing HPHT or CVD does not, by itself, describe the finished diamond's full appearance, measurements, clarity, or color assessment. Compare the actual reported characteristics and the stone itself.

If a seller argues that a method automatically makes every diamond superior, ask for the evidence relevant to the particular item.

Read the report's scope

Some report products include information about growth method or post-growth treatment, while others may present a different type of assessment. Look for the information explicitly rather than assuming it is included.

If the document does not answer your question, contact the issuing laboratory or discuss the appropriate examination with a gemological professional.

Compare stones as individual items

Keep the origin designation, report number, applicable results, measurements, and comments together. Then consider the actual appearance and intended jewelry design.

A growth-method term is useful context. It becomes more meaningful when it stays connected to the complete description of the diamond.

Further reading: GIA: HPHT and CVD growth processes