What Is a Synthetic Diamond?
A synthetic diamond (laboratory-grown) is not an imitation of diamond. It is crystalline diamond material produced through a human-controlled technological growth process, most commonly the HPHT or CVD method.
That statement has two equally important parts. The first concerns the material: its lattice is diamond, and the material can possess diamond’s fundamental physical properties. The second concerns origin: the crystal did not form through a natural geological process within Earth.
Considering only one of these two aspects leads to error.
Material Identity Is Not the Same as Origin
Four categories must be kept separate:
Natural diamond — diamond material formed through a natural geological process.
Synthetic diamond — diamond material produced through technological growth.
Treated diamond — an existing diamond whose property, such as color or the appearance of a fracture, has been altered by a subsequent process. Either a natural or a synthetic diamond can be treated.
Simulant — a material that imitates diamond’s appearance but is not crystalline diamond material. Cubic zirconia and moissanite are common examples of simulants.
“Is it diamond?” and “How did it form?” are two different questions.
What “the Same Material” Means
A synthetic diamond can share the following characteristics with a natural diamond:
- an sp³-bonded carbon lattice;
- very high hardness;
- a high refractive index;
- strong dispersion;
- high thermal conductivity;
- the characteristic Raman signal of diamond.
However, the growth process leaves different statistical patterns in impurities, growth sectors, luminescence, lattice strain, and other microscopic or spectroscopic features. Laboratory identification is based precisely on these differences.
HPHT and CVD—The Two Principal Methods
HPHT growth uses very high pressures and temperatures, a carbon source, a diamond seed, and usually a metal solvent-catalyst. Within a controlled temperature gradient, carbon dissolves and crystallizes on the seed.
CVD growth takes place at much lower pressure. A gas mixture—typically rich in hydrogen and containing a hydrocarbon such as methane—is activated by plasma. Reactive carbon species reach a heated diamond substrate and incorporate carbon into the crystal layer by layer.
These two technologies are discussed in detail in Chapters 49 and 50.
Seed, Growth, and the As-Grown State
Both principal technologies for commercial single-crystal growth use a diamond seed as the initial crystalline substrate.
The seed is not a finished stone that is merely “coated.” New diamond material grows from it in crystallographic continuity. Growth produces an as-grown crystal or plate that can subsequently be cut, treated, and polished.
It is therefore necessary to distinguish among:
- growth method;
- as-grown state;
- post-growth treatment;
- final polished product.
For example, a CVD diamond may undergo HPHT treatment after growth to alter its color. This does not make it an “HPHT-grown” diamond; its growth method remains CVD, while HPHT in this case is a treatment.
Synthetic Diamonds Are Not Uniform Commodities
A controlled process does not mean that every crystal is perfect. Synthetic diamonds vary in:
- color;
- clarity;
- lattice strain;
- impurity distribution;
- growth sectors and zones;
- post-growth processing;
- cutting quality;
- weight and dimensions.
Production can be controlled, but it does not produce atomically identical stones.
Diamond Type Is Not Proof of Origin
Many gem-quality CVD diamonds contain very little measurable nitrogen and are type IIa. HPHT material is often type Ib, but it can also be type IIa or IIb, depending on the process and intended result.
At the same time, natural type IIa and IIb diamonds also exist. FTIR typing can therefore provide highly useful screening data, but it is not a final verdict on natural versus synthetic origin.
Why the Unaided Eye Often Cannot Provide a Reliable Distinction
A well-cut synthetic diamond can look like a natural diamond with the same basic visual characteristics. Color, clarity, fire, and scintillation are not in themselves evidence of geological origin.
The claim that “an experienced jeweler can tell immediately” is not reliable as a general rule. Microscopic features can be indicative, but modern identification increasingly requires spectroscopic and luminescence analysis.
A standard thermal diamond tester primarily helps confirm that the material is diamond; it does not prove natural origin.
A Simulant Is Not a Synthetic Diamond
Moissanite is silicon carbide. Cubic zirconia is zirconium oxide. Both can visually imitate diamond, but their chemistry, structure, and physical properties differ.
It is therefore incorrect to call a simulant a “lab diamond.” A synthetic diamond and a diamond simulant belong to different categories.
Terminology Depends on the Standard and Jurisdiction
This book uses synthetic diamond as its primary term; at the first mention in each chapter, laboratory-grown is given in parentheses as an equivalent (ISO 18323:2015, clause 2.4 lists the terms as synonyms). The terms laboratory-created and synthetic diamond may also appear in international documents, depending on the applicable nomenclature system.
As of October 23, 2026, the following applies:
- ISO 18323:2015 remains the published international standard for consumer terminology relating to diamonds and was reconfirmed on February 19, 2026;
- the CIBJO Diamond Blue Book 2026-1 (September 2026, Vicenza; international voluntary trade standard) permits only the term synthetic diamond; laboratory-grown and laboratory-created are no longer CIBJO terms, but remain usable where national law allows them (e.g., the FTC Jewelry Guides in the United States);
- the U.S. FTC Jewelry Guides permit clear qualifiers such as laboratory-grown and laboratory-created when the material has essentially the same optical, physical, and chemical properties as a mined diamond; the Jewelry Guides are industry guidance interpreting the application of Section 5 of the FTC Act, not a standalone law;
- the previous CIBJO Diamond Blue Book 2024-1 (until September 2026) permitted synthetic, laboratory-grown, and laboratory-created as synonymous qualifiers; the July 2026 proposal to limit the 4Cs to natural diamonds is not confirmed as adopted.
Because standards can change, the web edition must keep this note dated.
Reports and Laser Inscriptions
A grading report can confirm synthetic origin and provide information within the scope of the specific service. A laser inscription on the girdle can link a stone to a report number and disclosure.
However, an inscription is not sufficient without a physical match. It can be removed, polished away, misread, or counterfeited. The document, weight, dimensions, inscription, and microscopic features should all agree.
Current GIA Practice Is Not a Universal Standard
Since October 1, 2025, GIA has used an overall Premium or Standard Quality Assessment classification for eligible colorless to near-colorless synthetic diamonds, rather than its traditional natural-diamond nomenclature. This is the policy of one institution during a particular period, not a definition of the material itself or a rule followed by every laboratory.
A full review of laboratory systems and reports appears in Chapters 54 and 75–77.
Origin Is Not a Value Judgment
Material identity does not automatically determine rarity, market price, resale liquidity, environmental footprint, or social impact.
Natural and synthetic diamonds have different production chains and different economics. Any claim that one category is “always more ethical,” “always greener,” or “always a better investment” requires separate data, methodology, and a dated factual cutoff.
Those questions are addressed in Chapters 55–56 and 94–95.
Professional Product-Verification Protocol
- Read the full product name.
- Determine whether the material is described as natural, synthetic, or simulated.
- Separately check for any treatment disclosure.
- Verify the institution, date, and type of report.
- Compare the documented weight and dimensions with the stone.
- Check the laser inscription when present.
- Physically match inclusions and other identifying features.
- For jewelry, determine whether all stones have the same origin.
- Keep quality claims separate from origin claims.
- Verify environmental, ethical, and provenance claims separately.
Chapter Summary
- A synthetic diamond is diamond material of synthetic origin.
- It is not a simulant merely because it is not natural.
- Material identity and mode of formation are two separate axes.
- HPHT and CVD are the two principal commercial growth technologies.
- A seed is the crystalline substrate on which new diamond material grows.
- The as-grown state must be distinguished from post-growth treatment.
- Synthetic diamonds vary in color, clarity, defects, and processing.
- Diamond type is not a conclusive origin test.
- The unaided eye and a standard diamond tester are often insufficient to determine origin.
- Moissanite and cubic zirconia are simulants, not synthetic diamonds.
- Terminology must be tied to a specific standard, jurisdiction, and date.
- Quality, value, sustainability, and origin must be evaluated as separate questions.
Sources for this chapter
Sources are primary or authoritative; the label in brackets gives the jurisdiction or source type.
- ISO: ISO 18323:2015 (jurisdiction: international)
- CIBJO: Diamond Blue Book 2026-1 (jurisdiction: international)
- CIBJO: CIBJO rules that ‘synthetic’ should be sole descriptor for created products with same chemical, physical and structural elements as natural equivalents (September 2026) (jurisdiction: international)
- FTC: Jewelry Guides, 16 CFR Part 23 (jurisdiction: USA; federal guides)
- GIA: GIA Launches Updated Laboratory-Grown Diamond Services October 1 (26 August 2025)
- GIA: HPHT and CVD Diamond Growth Processes