A lab-grown diamond is a man-made single crystal of pure carbon with the same essential cubic crystal structure, hardness and optical properties as a natural diamond. The current trade term is lab-grown; the FTC's revised Jewelry Guides published in 2018 explicitly permit lab-grown, laboratory-grown, laboratory-created, and the qualifier-followed-by-creator-name forms, while requiring that whichever term is used be clear, conspicuous and immediately adjacent to the word diamond.

Production methods

Two industrial processes dominate. High pressure, high temperature growth, abbreviated HPHT, places a small natural or synthetic diamond seed in a metal-flux capsule together with a carbon source, then subjects the assembly to pressures of around five to six gigapascals and temperatures of 1300 to 1600 degrees Celsius inside a belt, cubic or BARS press. Carbon dissolves in the molten metal and recrystallises on the seed, producing a cuboctahedral crystal whose growth-sector geometry is diagnostic. HPHT diamonds frequently contain trace nickel, iron or cobalt from the flux and may show metallic inclusions visible under magnification.

Chemical vapour deposition, abbreviated CVD, places a thin diamond seed plate in a low-pressure chamber filled with hydrogen and a small percentage of methane. A microwave or hot-filament source breaks the gases into reactive species, and carbon atoms deposit layer by layer onto the seed at temperatures around 800 to 1200 degrees Celsius. The resulting crystal is tabular, with a characteristic stripe or layer-cake growth structure visible under DiamondView ultraviolet imaging. Most CVD growth is followed by HPHT post-treatment to remove brown colour and lift clarity, a step now standard in commercial production.

Identification

Both HPHT and CVD lab-grown stones are routinely identified at gemmological laboratories. The diagnostic indicators include fluorescence patterns under short-wave ultraviolet (DiamondView shows the cuboctahedral cross or the CVD layer pattern), photoluminescence spectra at liquid-nitrogen temperature showing the silicon-vacancy doublet at 736.6 and 736.9 nanometres in CVD material or the nickel-related lines in HPHT, and growth-sector zoning visible in cathodoluminescence. The de Beers DiamondSure, DiamondView and SYNTHdetect screening instruments and the GIA iD100 and equivalent verification devices are widely used at the dealer level. Small melee, particularly below 0.05 carat, requires bulk screening since one-by-one testing is uneconomical.

Major laboratories now grade lab-grown diamonds on the same Four Cs scale used for natural diamonds, but issue them on visually distinct reports. GIA, IGI, GCAL and others laser-inscribe lab-grown into the girdle along with the report number.

Market history

General Electric produced the first reproducible synthetic diamond in 1954 using HPHT, but commercial gem-quality production took decades to develop. Sumitomo Electric and de Beers operated industrial-grade growers from the 1970s; gem-quality HPHT material became commercially significant in the 2000s through Russian, Ukrainian and Chinese producers. CVD gem production reached commercial scale in the late 2000s through Apollo Diamond, Gemesis and several Indian and Chinese companies, and grew rapidly through the 2010s as growth chambers became larger, faster and more reliable.

de Beers's launch of Lightbox in 2018 at a fixed price of 800 dollars per carat regardless of size or quality marked an explicit attempt to position lab-grown as a fashion category rather than a fine-jewellery store of value. Within five years, retail prices on natural-equivalent lab-grown rounds had collapsed by more than eighty percent, with one-carat G VS2 round brilliants moving from above 5000 dollars in 2018 to below 1000 dollars by 2024 in standard retail. The wholesale collapse was steeper still, and is discussed in the entries on lab-grown diamond price collapse and lab-grown vs natural debate.

Disclosure and consumer protection

Both the FTC Jewelry Guides in the United States and equivalent CIBJO and ISO standards internationally require unambiguous disclosure of lab-grown origin at every stage of trade and at retail. Use of unqualified terms such as cultured, real, genuine or simply diamond without the qualifier is not compliant. The trade has also seen aggressive policing by both the natural diamond council and the lab-grown trade associations against undisclosed mixing of lab-grown melee into natural-diamond parcels, a practice that the screening instruments above were specifically designed to detect.

Comparison with natural diamond

Optically and mechanically lab-grown and natural diamonds are indistinguishable in most respects: hardness 10 on Mohs, refractive index 2.418, dispersion 0.044. The differences are in growth history, trace impurities and economic profile rather than in appearance to the unaided eye. The price gap between equivalent natural and lab-grown stones, the absence of an organised secondary market for lab-grown, and the rapidly falling retail prices have produced markedly different positions in the gemmological and consumer markets, even though the physical objects are nearly identical.