A cultured diamond is a laboratory-grown diamond — chemically, physically, and optically identical to a diamond of natural geological origin — marketed under a term formally recognised by the United States Federal Trade Commission (FTC) as permissible, provided it is accompanied by clear disclosure of the stone's non-natural origin. The term sits alongside "laboratory-grown," "laboratory-created," and "[manufacturer name]-created" in the FTC's revised Jewellery Guides of 2018, which represent the most significant overhaul of US gemstone marketing regulation in decades. Understanding what "cultured diamond" means — and, equally, what it does not mean — is essential for retailers, gemmologists, and consumers navigating an increasingly complex marketplace.

The 2018 FTC Revision: What Changed

Prior to 2018, the FTC's Guides for the Jewellery, Precious Metals, and Pewter Industries defined a diamond strictly as a natural mineral, and the term "synthetic" was the principal qualifier applied to laboratory-grown material. The 2018 revision made several consequential changes. First, the FTC dropped the word "natural" from its definition of diamond, acknowledging that laboratory-grown diamonds share the same chemical composition (pure carbon in a cubic crystal structure), crystal habit, hardness (10 on the Mohs scale), refractive index (approximately 2.417), and thermal conductivity as their mined counterparts. Second, the Commission expanded the list of acceptable qualifying terms to include "cultured diamond" and "cultured" as a standalone modifier — a borrowing from the long-established vocabulary of the cultured-pearl trade, where the word signals human intervention in an otherwise natural process.

The FTC simultaneously reaffirmed that the unqualified term "diamond," used alone in a commercial context to describe a laboratory-grown stone, remains deceptive. Any permissible term must appear with a qualifier that clearly communicates the stone's origin. The Commission also confirmed that "synthetic diamond" remains technically permissible, though it noted industry objections to the term on the grounds that "synthetic" implies inferior or imitation material — a characterisation the FTC itself acknowledged was scientifically inaccurate, given that the stones are compositionally genuine diamonds.

Why "Cultured" Was Adopted

The laboratory-grown diamond sector — led by producers using High Pressure High Temperature (HPHT) and Chemical Vapour Deposition (CVD) methods — lobbied actively for the inclusion of "cultured" as an acceptable qualifier. The analogy to cultured pearls was deliberate: just as a cultured pearl is a genuine pearl produced with human assistance, a cultured diamond is a genuine diamond produced in a controlled technological environment rather than through geological processes over millions of years. Proponents argued that the term is both accurate and consumer-friendly, avoiding the negative connotations that some buyers associate with "synthetic" or "lab-grown."

Critics, including segments of the natural diamond trade, contended that the cultured-pearl analogy is imperfect. Cultured pearls involve a living organism and a natural biological process that is merely initiated by human intervention; laboratory-grown diamonds are produced entirely by industrial processes — either the HPHT method, which replicates the extreme pressures and temperatures of the Earth's mantle, or CVD, in which carbon-rich gases are deposited atom by atom onto a seed crystal in a plasma reactor. The FTC declined to adjudicate this philosophical debate, focusing instead on the practical requirement that consumers receive unambiguous disclosure of non-natural origin.

Permissible and Impermissible Terms Under the Guides

The 2018 Jewellery Guides establish a clear framework. The following qualifiers are explicitly permissible when used with "diamond" in a commercial context:

• Laboratory-grown
• Laboratory-created
• Cultured
• [Manufacturer name]-created (e.g., "Chatham-created diamond")
• Synthetic (permissible but disfavoured by much of the industry)

Terms that remain impermissible or that the FTC has identified as potentially deceptive include the unqualified use of "diamond" for laboratory-grown material, and any phrasing that implies geological or natural origin where none exists. The FTC has also cautioned against the use of "real diamond" or "genuine diamond" in ways that could mislead consumers into believing the stone was mined, even though laboratory-grown diamonds are, in a mineralogical sense, real and genuine diamonds.

It is worth noting that the FTC's jurisdiction is limited to the United States. Other regulatory bodies — including the European Commission and the UK's Advertising Standards Authority — have their own disclosure frameworks, which broadly align with the principle of clear origin disclosure but may differ in specific terminology requirements.

Gemmological Identity: Cultured vs. Natural Diamond

From a gemmological standpoint, a cultured (laboratory-grown) diamond is indistinguishable from a natural diamond by standard visual inspection, loupe examination, or conventional refractometry. Both are pure carbon crystallised in the isometric system; both exhibit the same adamantine lustre, the same dispersion (fire), and the same exceptional hardness. Distinguishing the two requires specialised laboratory equipment. HPHT-grown diamonds frequently display distinctive growth patterns visible under ultraviolet fluorescence, and may contain metallic flux inclusions not found in natural stones. CVD diamonds often show characteristic strain patterns and may exhibit unusual fluorescence or phosphorescence. Leading gemmological laboratories — including the Gemological Institute of America (GIA), the International Gemgemological Institute (IGI), and the Swiss Gemmological Institute (SSEF) — issue grading reports for laboratory-grown diamonds that explicitly state the growth method and origin, and the GIA has used the descriptor "Laboratory-Grown" on its reports since 2019.

The trade infrastructure surrounding disclosure has grown considerably since 2018. The Diamond Producers Association (now the Natural Diamond Council) and the International Grown Diamond Association (IGDA) have both published guidelines for their respective constituencies, and major retail chains have adopted point-of-sale disclosure protocols in response to FTC guidance.

Market Context and Trade Usage

In practice, "cultured diamond" is used more commonly in marketing materials and retail contexts than in gemmological laboratory reports, where "laboratory-grown" remains the dominant term. The distinction matters: a grading report from GIA or IGI will not use "cultured diamond" as its primary descriptor, whereas a retailer's display card or website may do so, provided the accompanying disclosure is clear. The term has gained particular traction among producers and retailers seeking to position laboratory-grown diamonds as a premium, consciously chosen product rather than a budget substitute — a positioning strategy that the FTC's acceptance of the "cultured" analogy has, at least implicitly, facilitated.

Wholesale and auction markets have been slower to adopt the term. Major auction houses — Christie's, Sotheby's, Bonhams — typically describe laboratory-grown diamonds in their catalogues using "laboratory-grown" or "synthetic," reflecting the conventions of the international trade and the expectations of a collector audience for whom precise, unambiguous terminology is paramount.

Further Reading

• FTC: Revised Jewellery Guides, Federal Register Notice, 2018
• GIA Gems & Gemology: Laboratory-Grown Diamond Disclosure (Fall 2018)
• GIA: Laboratory-Grown Diamonds