Lab-Grown Diamonds and Synthetic Gems: What Indian Jewellers Need to Know About Testing

The rapid growth of lab-grown diamonds and synthetic gemstones in the Indian market has created new challenges and opportunities for jewellers, testing laboratories, and consumers. Understanding the differences between natural and lab-grown stones, and the testing methods available for identification, is essential for maintaining transparency and trust.

Lab-Grown vs Natural Diamonds

Natural diamonds form over billions of years under extreme heat and pressure deep within the Earth's mantle. They are mined, cut, and polished for use in jewellery.

Lab-grown diamonds (also called synthetic, man-made, or cultured diamonds) are produced in laboratories using two primary methods:

HPHT (High Pressure High Temperature) — Replicates the natural formation conditions by subjecting carbon to extreme pressure (over 5 GPa) and temperature (over 1,400°C) in the presence of a metal catalyst.

CVD (Chemical Vapour Deposition) — Grows diamond crystals from a carbon-rich gas mixture in a vacuum chamber. A diamond seed crystal is placed in the chamber, and carbon atoms from the gas attach to it layer by layer.

Both methods produce diamonds that are chemically, physically, and optically identical to natural diamonds. They have the same crystal structure, hardness (10 on the Mohs scale), refractive index, and thermal conductivity.

Why Testing Matters

Since lab-grown diamonds share virtually all physical and chemical properties with natural diamonds, standard gemological tools cannot distinguish them. A 10x loupe, a refractometer, and standard thermal testers will produce identical results for both types. Advanced laboratory testing is required for definitive identification.

Testing Methods for Identification

Spectroscopic analysis — Advanced spectroscopy techniques (UV-visible, infrared, and photoluminescence spectroscopy) can detect growth characteristics specific to each formation method. HPHT diamonds show metallic flux inclusions and specific nitrogen patterns. CVD diamonds exhibit characteristic silicon-vacancy centres and strain patterns.

DiamondView and similar instruments — Specialised instruments from organisations like De Beers (the DiamondView) use short-wave UV fluorescence imaging to reveal growth patterns that differ between natural and lab-grown stones.

Microscopic inclusions — Under high magnification, trained gemologists can sometimes identify growth-method-specific inclusions. HPHT stones may contain metallic flux remnants; CVD stones may show striation patterns.

India's Lab-Grown Diamond Industry

India has emerged as a major player in the global lab-grown diamond market, particularly in Surat, which is already the world's diamond cutting and polishing capital. Indian manufacturers have rapidly adopted CVD technology, and the country now produces a significant share of global lab-grown diamond output.

The Lab Grown Diamond and Jewellery Promotion Council (LGDJPC) under the Ministry of Commerce actively promotes the sector. India's lab-grown diamond exports have grown substantially, making it an important segment of the gems and jewellery trade.

Disclosure Requirements

Transparency is legally required. The Federal Trade Commission (US) and similar bodies worldwide require clear disclosure of whether a diamond is natural or lab-grown. In India, BIS and the Gem & Jewellery Export Promotion Council guidelines mandate accurate disclosure.

Jewellers must clearly label lab-grown diamonds as such on invoices, product labels, and marketing materials. Using terms like "real diamond" or "genuine diamond" for lab-grown stones without the "lab-grown" qualifier is misleading and potentially illegal.

Impact on the Gold Jewellery Market

For hallmarking centres and gold jewellery dealers, the lab-grown diamond trend has several implications:

Pricing — Lab-grown diamonds typically cost 60–80% less than natural diamonds of equivalent quality. This has made diamond-studded gold jewellery more accessible, potentially increasing demand for gold jewellery hallmarking.

Combined testing — Jewellery combining hallmarked gold with lab-grown diamonds requires both gold purity certification (BIS hallmarking) and accurate diamond disclosure.

Consumer education — Consumers increasingly need guidance on what they are buying. Jewellers who provide transparent information about both the gold purity (verified by hallmark) and the stone type (natural vs lab-grown) build stronger trust.

What Jewellers Should Do

Establish clear sourcing — Know your stone suppliers and obtain documentation confirming whether stones are natural or lab-grown.

Disclose accurately — Mark all lab-grown stones clearly on invoices and labels. Use BIS-compliant hallmarking for the gold component.

Stay informed — The technology and regulations in this space are evolving rapidly. Industry body communications and BIS updates are essential reading.

Consider offering both — Many consumers actively seek lab-grown diamonds for ethical or price reasons. Offering both natural and lab-grown options with full transparency can broaden your customer base.

The Bigger Picture

The growth of lab-grown diamonds does not diminish the importance of gold hallmarking — if anything, it reinforces it. As the gemstone component of jewellery becomes more complex, the independently verified gold purity certification provided by BIS hallmarking becomes an even more important anchor of consumer trust.