Synthetic diamond identification, treatments & composite stones

Free FGA-aligned treatments and synthetics reference

Modern lab-grown synthetic diamond (both HPHT, high-pressure / high-temperature, and CVD, chemical vapour deposition) is gemmologically identical to natural diamond by routine refractive index and specific gravity measurement, so identification depends on photoluminescence, short-wave UV fluorescence (DiamondView), and subtle defect-centre patterns visible only with laboratory instruments. The same is true for treated coloured stones: beryllium lattice diffusion, lead-glass fracture filling, flux-grown synthetic corundum, and hydrothermal synthetic emerald all require informed microscopy and, for the most ambiguous cases, FTIR / Raman / LA-ICP-MS analysis. This hub collects the 7 FGA-aligned articles on these topics, plus a one-page detection matrix covering the eleven highest- stakes materials a gemmologist encounters in commercial practice. Disclosure of treatment and synthetic origin is required by LMHC, GIA, and CIBJO standards, so confident identification is a commercial as well as an educational skill.

Eleven-material detection matrix

Material Primary test Diagnostic finding Confidence
HPHT synthetic diamond DiamondView short-wave UV imaging Yellow / green-blue cross-shaped fluorescence pattern along {100} growth sectors High (lab-only)
CVD synthetic diamond Photoluminescence (PL) at liquid-N₂ temperature Si-V centre at 737 nm doublet; Ni and N-related defect pattern differing from natural High (lab-only)
HPHT-treated natural diamond PL + UV-Vis-NIR; sometimes microscopy Removed brown colour from Type IIa; reduced 415 nm Cape line; stress-related graining High (lab-only)
Heat-treated ruby / sapphire Microscopy (10–40×) for altered inclusions Discoid stress fractures, melted / re-crystallised silk, partially-dissolved rutile High (gemmologist)
Beryllium-diffused sapphire LIBS or LA-ICP-MS for Be at >5 ppm Padparadscha-style orange-pink colour rim; concentric colour zoning under microscope Definitive (lab-only)
Lead-glass-filled ruby Darkfield microscopy + reflected light Blue / orange flash effect at fracture interfaces; trapped gas bubbles; lower lustre patches High (gemmologist)
Flux-grown synthetic corundum (Chatham, Kashan, Knischka) Microscopy Flux fingerprints (twisted veils), platinum platelets, hexagonal growth zoning High (gemmologist)
Flame-fusion (Verneuil) corundum / spinel Microscopy + polariscope Curved colour bands; gas bubbles in clouds; tabular elongation pattern Definitive (gemmologist)
Hydrothermal synthetic emerald (Biron, Lechleitner, Tairus) Microscopy + RI Chevron growth structure, two-phase nail-head inclusions, slightly lower RI than natural High (gemmologist)
Garnet-topped doublet Microscopy (immersion in water) Red reflection from garnet crown; cement plane with gas bubbles; girdle separation Definitive (gemmologist)
Opal triplet Side-view immersion microscopy Three layers: black base, thin opal slice, transparent dome (quartz / glass) Definitive (gemmologist)

For evidence-weighted detection across multiple clues, try the Treatment Wizard (18 clues × 11 treatments, weighted scoring) and the Treatment Detection table.

Deep-dive treatment / synthetic articles

Beryllium Diffusion: Deep Diagnostic Reference

Full per-method detection protocol for beryllium lattice diffusion in corundum, with disclosure standards and stability data.

advanced

CVD Diamond Detection: Deep Diagnostic Reference

Full detection protocol for CVD synthetic diamonds, distinguishing from natural and HPHT-treated stones using DiamondView, FTIR, and photoluminescence.

advanced

HPHT Diamond Treatment: Deep Diagnostic Reference

Full detection protocol for HPHT-treated natural diamonds, including type-by-type outcomes, DiamondView patterns, and photoluminescence signatures.

advanced

Lead Glass-Filled Ruby: Deep Diagnostic Reference

Full detection protocol for composite (lead glass-filled) ruby, with nomenclature, durability, and disclosure standards.

advanced

Foundation overview articles

Composite Stones

Doublets, triplets, assembled stones, and their detection including opal doublets, garnet-topped doublets, and soudé emeralds.

intermediate

Synthetic Gemstones

Synthetic gem production methods including flame fusion, hydrothermal, flux growth, and detection techniques.

advanced

Disclosure and lab reports

Treatment and synthetic-origin disclosure is required practice across the trade. Major laboratories use harmonised terminology defined by the Laboratory Manual Harmonisation Committee (LMHC):

  • Treatments are reported with type, extent, and permanence on every coloured-stone report.
  • Synthetic stones are labelled "synthetic" or "laboratory-grown"; the term "cultured" is reserved for pearls.
  • Composite materials (doublets, triplets, lead-glass-filled ruby) must be sold under their composite identification, never as the parent species alone.
  • See our disclosure article for a full breakdown of trade-practice requirements by jurisdiction.