What Counts as a Diamond: The FTC Jewelry Guides Explained

The FTC Jewelry Guides are codified at 16 CFR Part 23 and apply to advertising, marketing, and product description in the jewellery industry¹. The Jewelry Guides are not statute law but interpret the FTC Act's prohibition on unfair or deceptive practices in the specific commercial context of jewellery.

The 2018 revision was the first substantial update in nearly twenty years. Two changes were significant for the lab-grown industry. First, the FTC removed the word natural from its long-standing definition of diamond, which had previously read "a natural mineral consisting essentially of pure carbon crystallized in the isometric system"³. The revised definition no longer requires natural origin. The mineralogical and crystallographic content of the definition stands; the origin requirement was removed.

Second, the FTC updated its guidance on terminology. It recognised that laboratory-grown diamonds, which are physically and optically the same material as mined diamonds, fall within the revised definition. The revision was widely covered in trade press as the moment lab-grown diamonds were officially diamonds in US commerce⁴⁵.

The Jewelry Guides set out specific disclosure language for laboratory-grown stones¹². The FTC's plain-language consumer guidance, In the Loupe, summarises the rule as follows: "If a product is being marketed as a diamond and is laboratory created, that fact must be clearly and conspicuously disclosed."

The recommended qualifiers are:

• Laboratory-grown
• Laboratory-created
• [Manufacturer name]-created (for example, Lightbox-created)
• or any other equivalent term that clearly conveys the laboratory origin

The qualifier must appear immediately preceding the word diamond and must be displayed with equal conspicuousness. A retailer cannot satisfy the rule by burying laboratory-grown in fine print at the bottom of a webpage while showing diamond in large type at the top. Both must be at the same visual prominence in the relevant context.

Before 2018, the FTC's recommended terminology for laboratory-grown stones included the word synthetic. The 2018 revision removed it². The reason was consumer research: a meaningful proportion of consumers interpreted synthetic as imitation, conflating laboratory-grown diamonds with cubic zirconia or moissanite. Removing synthetic from the recommended list was meant to reduce that confusion.

The word was not banned. Trade publications, scientific literature, and gemmological practice continue to use synthetic in its established technical sense to mean laboratory-grown. The FTC's enforcement focus is on the deceptive use, where a marketer implies that a competitor's laboratory-grown stone is not really a diamond by calling it synthetic without further qualification, which contradicts the regulatory recognition that laboratory-grown diamonds are diamonds.

The word cultured is permitted as a description of laboratory-grown diamonds, but only when accompanied by a primary qualifier¹. A retailer may describe a stone as a cultured diamond only if it also says laboratory-grown, laboratory-created, or [manufacturer]-created with equal conspicuousness. Cultured cannot stand alone as the qualifier, because the Jewelry Guides require the laboratory origin to be plain to a reasonable consumer.

The Jewelry Guides treat diamond simulants as a separate category from laboratory-grown diamonds¹. A simulant is a material that looks like a diamond but is chemically and physically different. The most common are cubic zirconia (zirconium dioxide), moissanite (silicon carbide), and white sapphire (corundum, aluminium oxide). None of these are pure carbon, and none of them have the diamond cubic crystal structure. They are not diamonds under the FTC definition, and selling them as diamonds, with or without a laboratory-grown qualifier, is deceptive.

The trade-acceptable description of these materials is diamond simulant, cubic zirconia (CZ), moissanite, or simulated diamond, depending on context⁶. Calling moissanite a synthetic diamond is, under current FTC interpretation, deceptive: moissanite is not a diamond at all.

The Jewelry Guides also require disclosure of treatments that affect the appearance, value, or durability of a stone¹. For both natural and laboratory-grown diamonds, common treatments include HPHT colour treatment (post-growth high-pressure-high-temperature processing to remove brown tints), laser drilling to lighten dark inclusions, and fracture filling to improve clarity. Treatments must be disclosed in advertising and on the report. The disclosure must be specific enough that a consumer can understand what was done and how it affects the stone.

The FTC has used warning letters and consent orders rather than litigation to push compliance. Trade press has reported letters sent to laboratory-grown sellers about insufficiently conspicuous qualifiers, and to large retailers about advertising language that implied a stone was natural when it was laboratory-grown⁴⁵. The pattern is consistent: the FTC asks for the qualifier to be added or made more visible, and most parties comply without contested proceedings.

The wider effect of FTC enforcement is to push the entire industry toward standardised, plain-language disclosure. A consumer reading a current advertisement for a laboratory-grown engagement ring should see laboratory-grown diamond or laboratory-created diamond at the same visual weight as the rest of the description. If they see only diamond with the laboratory origin in fine print, the marketer is out of step with the rule.

Where this fits in the reference

The FTC rules are the regulatory backstop. The market is shaped by them but also by independent grading laboratories (Chapter 4, Chapter 5) and by production economics (Chapter 7). Chapter 13 covers identification methods that ensure the disclosure rules can be enforced even when paperwork is missing.