Lab-grown diamonds (also called synthetic, cultured, or created diamonds) are chemically, physically, and optically identical to natural diamonds. As the lab-grown market explodes, certification and disclosure have become critical. This guide covers how lab-grown diamonds are certified, the two main growth methods, and what buyers and sellers need to know.
What Are Lab-Grown Diamonds?
Lab-grown diamonds are real diamonds created in a laboratory environment using advanced technology that replicates the natural diamond-growing process. They have the same chemical composition (carbon), crystal structure, hardness (10 Mohs), and optical properties as natural diamonds. The only difference is origin: one grew deep in the Earth over billions of years, the other grew in a lab in weeks.
- Chemical composition - Pure carbon (C), same as natural diamond
- Hardness - 10 on Mohs scale (same as natural)
- Refractive index - 2.42 (same as natural)
- Dispersion - 0.044 (same as natural)
- Growth time - Weeks to months (vs billions of years natural)
- Cost - 30-70pct less than natural diamonds of same quality
Two Growth Methods
HPHT (High Pressure High Temperature)
HPHT mimics the natural diamond-growing conditions by applying extreme pressure (5-6 GPa) and temperature (1300-1600C) to a diamond seed. Carbon dissolves in molten metal (iron, nickel, cobalt) and crystallizes on the seed.
- Invented - 1954 (GE, first commercial production)
- Equipment - Belt press, cubic press, or BARS press
- Growth time - Days to weeks
- Color - Often brownish/yellowish due to nitrogen; can be treated to colorless
- Identification features - Metallic inclusions (flux), irregular growth patterns
- Cost - Lower equipment cost, higher energy cost
- Best for - Colored diamonds (yellow, blue), smaller sizes
CVD (Chemical Vapor Deposition)
CVD grows diamonds by depositing carbon from a gas mixture (methane + hydrogen) onto a diamond substrate in a vacuum chamber. Microwaves or heat create plasma that breaks down the gas, allowing carbon atoms to settle and form diamond.
- Invented - 1980s, commercialized 2000s
- Equipment - Microwave plasma reactor
- Growth time - Weeks to months
- Color - Can produce colorless more easily than HPHT; may have pink/brown tint
- Identification features - Strain patterns, graphitic inclusions, layered growth
- Cost - Higher equipment cost, lower energy cost
- Best for - Colorless diamonds, larger sizes, jewelry quality
| Factor | HPHT | CVD |
|---|---|---|
| Growth mechanism | High pressure + temperature | Gas deposition in vacuum |
| Typical color | Yellow/brown (treatable) | Colorless/pink/brown |
| Inclusions | Metallic flux inclusions | Graphitic, non-metallic |
| Size capability | Up to ~10ct (gem quality) | Up to ~15ct+ (gem quality) |
| Market share | ~40pct | ~60pct (growing) |
| Post-growth treatment | Often HPHT annealing for color | Often HPHT treatment to remove brown |
How Labs Identify Lab-Grown Diamonds
Gemological labs use several techniques to distinguish lab-grown from natural diamonds:
- Fluorescence patterns - Lab-grown diamonds often show distinctive fluorescence under UV (crosshatch, cuboctahedral patterns)
- Phosphorescence - Some lab-grown diamonds glow after UV light is removed
- Inclusion types - HPHT has metallic inclusions; CVD has graphitic inclusions
- Growth structures - Lab-grown shows distinct growth zoning
- Spectroscopy - FTIR and UV-Vis spectroscopy reveal differences in nitrogen and defects
- PL spectroscopy - Photoluminescence identifies specific defects (Si-V, NV centers)
- DiamondView - UV fluorescence imaging reveals growth patterns
Lab-Grown Diamond Certification
IGI (International Gemological Institute)
IGI is the leading certifier of lab-grown diamonds, with approximately 70pct market share. IGI lab-grown reports include:
GIA (Gemological Institute of America)
GIA certifies lab-grown diamonds but with a distinct report format. GIA lab-grown reports:
AGS and Other Labs
AGS Laboratories also certifies lab-grown diamonds using the same standards as natural. NGTC (China) certifies lab-grown diamonds and marks them as "synthetic diamond" or "lab-grown diamond."
Disclosure Requirements
- US (FTC) - Must disclose lab-grown origin; terms like "real," "genuine," or "natural" are prohibited for lab-grown
- EU - Must disclose as "synthetic" or "lab-grown"; "cultured" is acceptable
- China - Must label as "synthetic diamond" (合成钻石) or "lab-grown"
- India - Must disclose and certify lab-grown diamonds
- Industry self-regulation - Many retailers voluntarily disclose even where not legally required
- Laser inscription - Most labs require "LAB GROWN" inscription on girdle
Grading Lab-Grown vs Natural Diamonds
Lab-grown diamonds are graded using the same 4Cs scale as natural diamonds, but there are some differences:
Post-Growth Treatments
Many lab-grown diamonds undergo post-growth treatment to improve color:
Certification for Wholesale
- IGI is standard - Most wholesale lab-grown diamonds come with IGI certificates
- Cost savings - IGI certification is cheaper and faster than GIA
- Laser inscription - Always verify "LAB GROWN" inscription
- Report verification - Verify all certificates online before purchasing
- Treatment disclosure - Ensure certificates disclose any HPHT post-growth treatment
- Brand vs unbranded - Branded lab-grown (Lightbox, Diamond Foundry) may not need certificates; unbranded should always be certified
Common Lab-Grown Certification Issues
- Passing as natural - Unscrupulous sellers may try to sell lab-grown as natural; always check for laser inscription and certificate
- Undisclosed treatments - HPHT post-growth treatment of CVD diamonds may not be disclosed by all sellers
- Fake certificates - Always verify certificates on the official lab website
- Grade inflation - Some smaller labs may grade lab-grown more leniently; stick to IGI/GIA/AGS
- Mixed parcels - Some parcels may contain both natural and lab-grown; test each stone
Frequently Asked Questions
What is the difference between CVD and HPHT lab-grown diamonds?
CVD (Chemical Vapor Deposition) grows diamonds from carbon gas in a vacuum chamber, producing mostly colorless stones with graphitic inclusions. HPHT (High Pressure High Temperature) grows diamonds under extreme pressure/temperature using molten metal flux, often producing yellow/brown stones with metallic inclusions. CVD currently holds about 60pct market share and is preferred for colorless jewelry diamonds. HPHT is often used for colored diamonds and smaller sizes. Both produce real diamonds - the choice depends on desired color, size, and budget.
Are lab-grown diamonds certified the same as natural diamonds?
Lab-grown diamonds are graded using the same 4Cs (color, clarity, cut, carat) as natural diamonds, but certificates clearly identify them as 'Laboratory Grown' and include the growth method (CVD or HPHT) and any post-growth treatments. IGI is the leading certifier (approximately 70pct market share), followed by GIA and AGS. Most lab-grown diamonds are laser-inscribed with 'LAB GROWN' on the girdle. The grading standards are identical, but the certificate format and disclosure requirements differ.
Do lab-grown diamonds need to be disclosed as lab-grown?
Yes, legally in most jurisdictions. In the US, the FTC requires disclosure of lab-grown origin and prohibits using terms like 'natural,' 'genuine,' or 'real' without qualification. The EU, China, and India also require disclosure. Most reputable labs laser-inscribe 'LAB GROWN' on the girdle. For wholesale and retail, always disclose lab-grown origin clearly - failure to do so can result in legal penalties and reputational damage.
Which certification is best for lab-grown diamonds?
IGI is the standard for lab-grown diamond certification, with approximately 70pct market share, lower cost, and faster turnaround. GIA also certifies lab-grown diamonds (digital-only reports) but is more expensive. AGS is another option, especially for cut-quality focus. For wholesale jewelry, IGI certification is sufficient and most cost-effective. Always verify certificates online and check for the 'LAB GROWN' laser inscription on each stone.
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