Not All Diamonds Are What They Appear

Some diamonds on the market have been treated to improve their appearance. These treatments can make lower-quality diamonds look better than they actually are, and they affect price and durability. Every buyer should understand what treatments are, which ones are acceptable, which ones are concerning, and how to identify them on a certificate.

What Treatments Are

Diamond treatments are processes applied to a diamond to change its appearance. Some treatments are permanent; others are not. Some treatments are widely accepted in the industry; others are considered controversial. The key principle: a treated diamond should always cost less than an equivalent untreated diamond, and all treatments must be disclosed on the certificate.

Common Treatments

HPHT Annealing

HPHT (High Pressure High Temperature) annealing is used to improve the color of diamonds. It can turn brown diamonds white or enhance the color of lower-color diamonds to make them appear higher. The process mimics what happens in the earth is mantle over geological time, but compressed into weeks in a laboratory.

HPHT-treated diamonds are generally stable and durable. The treatment is considered acceptable in the industry and is routinely disclosed on certificates. The main concern is price: an HPHT-treated diamond should cost significantly less than an equivalent untreated diamond of the same appearance.

Irradiation

Irradiation is used to create fancy color diamonds—green, blue, brown, pink, and other colors—by exposing the diamond to radiation that changes its crystal structure and color. Natural green and blue diamonds are created by similar radiation exposure over millions of years.

Irradiated diamonds are stable and durable for everyday wear. The treatment is considered acceptable and is routinely disclosed. Irradiated fancy color diamonds cost a fraction of natural fancy color diamonds of equivalent appearance.

Fracture Filling

Fracture filling is a treatment where a glass-like substance is injected into fractures in a diamond to make them less visible. The result can be dramatic—a diamond with visible fractures can look clean after treatment. This is the most controversial common treatment.

Fracture-filled diamonds carry significant concerns:

• Durability: The filling can be damaged by heat (such as a jeweler is torch during sizing) or by certain chemicals. If the filling is damaged, the fractures become visible again and the diamond is appearance is compromised.
• Detection: Fracture filling is difficult to detect without specialized equipment. A fractured-filled diamond may not be identifiable as such without gemological testing.
• Disclosure: While fracture filling should always be disclosed, some sellers do not disclose it, leaving buyers with a diamond they do not know has been treated.

We generally recommend avoiding fracture-filled diamonds. The durability risk is real and the value retention is poor.

Laser Drilling

Laser drilling is used to remove dark inclusions from diamonds. A microscopic laser burns a tiny channel from the surface to an inclusion, which can then be bleached or removed. The result is a cleaner-looking diamond.

Laser drilling is considered acceptable by the trade and is routinely disclosed. The tiny channels are usually invisible to the naked eye but can be seen under magnification. The durability of laser-drilled diamonds is not significantly affected—the channels are extremely small.

Coating

Diamond coating involves applying a thin layer of material (such as a polymer or lacquer) to the surface of a diamond to improve its color or add color. This is the least stable and least accepted treatment in the industry.

Coatings can wear off over time, particularly on the facets that receive the most wear. They can also be damaged by heat or chemicals. Coated diamonds should be clearly disclosed and priced significantly below equivalent untreated diamonds.

How to Identify Treatments

The surest way to identify treatments is to read the certificate carefully. GIA and IGI both require disclosure of any treatments on the certificate. Look for a comments section that mentions treatments, enhancements, or processing.

If a certificate does not mention any treatment, it could mean either that the diamond is untreated or that the laboratory did not detect a treatment. Reputable sellers will disclose treatments even if the certificate does not mention them.

The Price Impact of Treatments

Here is the key principle: a treated diamond should cost less than an equivalent untreated diamond. If you are paying untreated prices for a treated diamond, you are being overcharged.

The exact discount depends on the treatment and its impact on durability. HPHT annealing and irradiation create beautiful results with minimal durability concerns, so discounts may be moderate. Fracture filling creates real durability concerns, so discounts should be substantial.

The Disclosure Question

Federal Trade Commission guidelines in the United States require that gemstone treatments be disclosed at the point of sale. This applies to diamonds as well as other gemstones. A seller who does not disclose treatments is violating FTC guidelines.

If a seller cannot tell you whether a diamond has been treated, or if the certificate does not mention treatments when you suspect one may be present, that is a red flag. Walk away from any seller who is not transparent about treatments.

Lab-Grown Diamonds and Treatments

Lab-grown diamonds can receive the same treatments as mined diamonds. HPHT annealing is commonly used to improve the color of lab-grown diamonds. This should be disclosed on the certificate.

When buying a lab-grown diamond, check the certificate for any mention of treatments. If a lab-grown diamond has been treated, it should cost less than an equivalent untreated lab-grown diamond of the same quality.

At Aranc

We disclose all treatments on all our diamonds, whether mined or lab-grown. We do not sell fracture-filled diamonds due to the durability concerns. If you have questions about a specific treatment or want to know whether a particular diamond has been treated, our team is happy to help you understand the certificate and the facts.