CVD laboratory grown diamonds are the same as natural diamonds in all physical, chemical, and optical properties. CVD diamonds are classified as Type IIa diamonds which are the most chemically pure diamonds in the world. Type IIa diamonds also can be found in nature but are quite rare. As it pertains to natural earth mined diamonds, less than 5% are type IIa. Therefore, in reference to quality, since CVD laboratory grown diamonds are all type IIa, they are among the highest quality diamonds available on the market, regardless of origin. There is no way to differentiate a natural diamond from a CVD laboratory grown diamond to the naked eye, even for a Graduate Gemologist. Additionally, a standard diamond tester will not be able to differentiate whether a diamond is CVD grown or Natural, both will test as natural diamond. To accurately determine that a CVD diamond is in fact CVD grown requires the use of very precise and expensive testing machinery.
The second way to grow gem grade laboratory grown diamonds is a process known as HPHT or High Pressure High Temperature. HPHT is the original way of growing laboratory grown diamonds, and the less expensive way of doing so. HPHT diamonds are considered Type II diamonds. Unlike CVD diamonds that are Type IIa diamonds, HPHT diamonds will not test as diamond with a standard diamond tester even though they are technically diamonds. This is due to the relatively high amount of impurities in the diamond crystal. Additionally, optically they often appear different than natural or CVD diamonds in that they may display what is called a blue nuance. As the name would imply, a blue nuance is a light blue color that often makes the diamond look milky or hazy. Due to their lower cost of production, as well as lower overall quality, HPHT grown diamonds are generally less expensive than CVD grown diamonds. If a jeweler doesn’t identify a lab grown diamond as being either CVD or HPHT, you can be relatively certain that it is HPHT.