Lab-Grown Diamonds

A brief guide to synthetic, imitation, and treated diamonds

At Sarine Labs, the first step in the grading process is diamond authentication and treatment detection. Detecting synthetic or treated diamonds is a highly specialized skill, demanding deep gemological knowledge and advanced equipment. In order to know whether a diamond is natural, lab grown, imitation or treated, it is important to understand the various types of diamond imitations on the market today.

Synthetic Diamonds (LGD)

Grown in a laboratory, synthetic diamonds are both chemically and structurally identical to natural diamonds, consisting of crystalized carbon. In the early part of the 1900s, the race to synthesize diamonds was marked by intense secrecy and competition, leading to conflicting claims about who achieved the milestone first. General Electric (GE) was widely recognized as the pioneer in synthetic diamond production, having successfully synthesized diamonds in 1954 using the high-pressure, high-temperature (HPHT) method. However, ASEA, a Swedish company (today ABB), claims to have synthesized diamonds a year earlier, in 1953, but kept their results confidential due to patent concerns. Additionally, Union Carbide claims to have grown the first synthetic polycrystalline diamonds by the chemical vapor deposition method (CVD) in 1952. These competing claims emphasize the fierce rivalry among companies during this groundbreaking era.

In the early years, synthetic diamonds were primarily polycrystalline or of low-quality monocrystalline form. It wasn’t until the 1970s that gem-quality synthetic diamonds were successfully grown using the HPHT method. The first gem-quality monocrystalline diamond produced through the chemical vapor deposition (CVD) method was achieved in 2003 by Apollo Diamond in the USA. Around the same time, Gemesis was producing yellow to orange color gem quality synthetic diamonds using the HPHT method.

Since 2014 the producers of synthetic diamonds have made steady progress. Today, near colorless diamonds can be grown with good color and clarity at much lower cost than natural diamonds, and in all sizes from extremely small (0.5 mm round brilliant cut) to over 10 carat. Particularly small-sized synthetic diamonds (melee diamonds) are produced in huge quantities for use in jewelry.

Diamond Treatments

Diamonds can be treated in a variety of ways to enhance or change their appearance. This may be done in order to hide inclusions or to make their appearance less obvious, known as ‘clarity enhancements.’ In addition, the color of a diamond may be changed to make the diamond more attractive and/or more marketable. There are three ways the clarity of diamonds is enhanced:

• Fracture filling
• Laser drilling
• Internal laser drilling

Color-treated diamonds are much more common than clarity-enhanced diamonds. There are a range of color treatments used, sometimes in combination. These include:

• Surface coating
• Annealing under inert atmosphere
• Irradiation by high-energy particles
• Irradiation followed by annealing
• HPHT (High Pressure High Temperature) treatment
• HPHT followed by irradiation/annealing
• Irradiation followed by HPHT treatment

Of these treatments, only HPHT treatment is of importance for colorless diamonds. Brown type IIa and low nitrogen type IaB diamonds can be decolorized by this treatment.