Why Diamonds Are Treated
A treatment is a deliberate intervention performed on an existing diamond in an attempt to change its appearance or certain gemologically relevant properties. This definition immediately distinguishes treatment from two other things: the origin of the material and the manufacturing process used to produce a polished stone.
A natural diamond may be untreated or treated. A laboratory-grown diamond may likewise be as-grown or subsequently treated. Treatment is therefore not a third kind of diamond between natural and laboratory-grown.
What treatment is not
Cutting and polishing change a stone’s geometry, but they are not ordinarily classified as gemological treatments. The same applies to routine cleaning, setting in jewelry, and standard servicing.
Recutting or repolishing can substantially change weight, appearance, and grades, but it is a manufacturing or restoration intervention, not necessarily a treatment in the sense of changing color or apparent clarity.
A laser inscription on the girdle serves identification and is likewise not a color or clarity treatment.
Why diamonds are treated
The principal commercial objective is to make a stone more desirable. This may be achieved by:
- reducing the visibility of a dark inclusion;
- reducing the contrast of a surface-reaching fracture;
- removing or weakening a brown component;
- creating or changing color;
- modifying surface appearance.
Such an intervention is not necessarily fraudulent. The problem arises when a treatment is concealed, described incorrectly, or credited with properties it does not possess.
Three working groups
Three groups are useful for the purposes of this book.
Clarity treatments primarily change the perception of internal characteristics. These include laser drilling and fracture filling.
Color treatments change absorption centers and perceived bodycolor. These include HPHT processing, irradiation and annealing, and combinations of those methods.
Surface modifications may change perceived color or appearance by applying material to the surface. Coating is examined in detail later.
These groups are not absolutely closed. One stone may have undergone more than one intervention.
Five questions that must never be combined
For a treated diamond, five questions must be answered separately:
- Is the material diamond?
- Is the diamond natural or laboratory-grown?
- Has it been treated?
- Which treatment was used, and how certain is the conclusion?
- What are the consequences for stability, care, grading, and market representation?
As an analytical record of two separate axes, the statement “natural crystal origin + HPHT treatment” is entirely valid. A commercial description, however, must comply with the applicable nomenclature: the CIBJO Diamond Blue Book 2024-1 requires the term treated diamond, with optional identification of the treatment type, and cautions against the expressions natural treated diamond and treated natural diamond because they may be misleading. For laboratory-grown material, growth origin and post-growth treatment also remain separate pieces of information.
Detection is not disclosure
Detection is the technical process by which a treatment is established.
Disclosure is the communicative and, depending on the jurisdiction, legal obligation to make a known intervention clear to a buyer or another participant in the supply chain.
A laboratory may detect a treatment that the seller did not disclose. Conversely, a seller must not treat laboratory detection as a substitute for the seller’s own obligation to describe the goods correctly.
Stability is not one word
A treatment may be:
- physically permanent once the modification has been made;
- stable during normal wear but sensitive to jewelry work;
- sensitive to heat, chemicals, UV, ultrasonic cleaning, or steam;
- partially reversible or degradable;
- combined with another treatment that has a different stability profile.
The words stable and permanent should therefore be tied to the specific treatment and specific conditions, not used as blanket assurances of safety.
Stable color also does not mean that the stone itself is mechanically invulnerable. A feather, cavity, or thin edge exists independently of treatment status.
Treatment status is not a grade
Laser drilling may leave a drill hole that contributes to clarity assessment, but the word “laser-drilled” is not itself a clarity grade.
Fracture filling may visually reduce the contrast of a fracture, but the filler does not restore the original crystal lattice or erase the fact that the fracture exists.
HPHT treatment may change color, but the diamond’s natural origin remains unchanged.
Treatment, color grade, clarity grade, and durability must therefore be recorded as separate conclusions.
The U.S. disclosure framework
As of the factual cutoff of August 7, 2026, 16 CFR § 23.24 in the FTC Jewelry Guides identifies three separate reasons why failure to disclose a treatment would be unfair or deceptive: the treatment is not permanent, creates special care requirements, or has a significant effect on the stone’s value. The rule applies to sellers at every level of trade; for products that can be purchased without personal inspection, such as online sales, disclosure should appear in the solicitation or product description itself.
This is a U.S. regulatory framework and should not be presented as global law. Other markets may use different legal formulations.
The CIBJO Diamond Blue Book 2024-1 is broader in terminology: a treated diamond should be clearly described as a treated diamond, the word treated must not be concealed or abbreviated, and special care requirements must be disclosed. CIBJO is a professional and trade standard subject to local regulations, not a substitute for them.
Current GIA laboratory practice
As of August 7, 2026, GIA publicly states that it issues reports for diamonds with certain stable treatments, including irradiation, annealing, laser drilling, and HPHT processing, with disclosure of the known treatment. Grading reports are not issued for nonpermanent or unstable treatments such as fracture filling and coating.
GIA also requires submitters to disclose a known or even suspected treatment or synthesis when submitting material to the laboratory. This is GIA’s service policy and submission rule, not a universal rule for all laboratories or a substitute for a seller’s commercial disclosure obligation.
When treatments are combined
Laser drilling may be performed to gain access to a dark inclusion, while the same or another surface-accessible fracture may subsequently be filled. Color treatment may likewise involve sequences of different processes.
Discovering one treatment therefore does not end the examination. The professional question is: what has been done to the stone in its entirety?
Detailed pathways follow in Chapters 58–63.
Practical disclosure protocol
Before sale or servicing, it is useful to:
- confirm the identity of the material;
- establish natural or laboratory-grown origin;
- examine the existing report and the actual stone;
- separately record every known or suspected treatment;
- establish stability and special care requirements;
- refer the stone to a laboratory when necessary;
- use the precise treatment name rather than the vague term “enhanced” without explanation;
- carry treatment information forward in documentation and service history.
The most important rule is: unknown treatment status is not the same as an untreated stone.
Chapter summary
- A treatment is a deliberate post-growth change made to an existing diamond.
- A natural diamond can be treated and remain natural.
- A laboratory-grown diamond can be treated and retain its growth method.
- Cutting, cleaning, setting, and an identification inscription are not in themselves gemological treatments.
- Clarity, color, and surface treatments have different objectives and risks.
- Treatment is not synonymous with fraud; incorrect or omitted disclosure can be a regulatory and commercial problem.
- Detection and disclosure are two separate functions.
- Treatment status is not the same as a color or clarity grade.
- Stability and care requirements must be determined for the specific treatment.
- One diamond can have multiple combined treatments.
- GIA currently reports certain stable treatments such as irradiation, annealing, laser drilling, and HPHT, but does not issue a grading report for fracture-filled or coated diamonds.
- A professional description should separate identity, origin, treatment, grade, durability, and market representation.
[VISUAL 57.1: Four separate axes—natural/laboratory-grown origin, treatment, grade, and durability]
[VISUAL 57.2: Treatment map for Chapters 58–63—laser drilling, fracture filling, HPHT, irradiation/annealing, coating, and combinations]
[VISUAL 57.3: Detection versus disclosure—laboratory evidence and commercial communication as separate flows]
[VISUAL 57.4: Treatment-disclosure workflow—identity → origin → treatment → stability/care → documentation]