Diamond

Related: Diamond Varieties

Blue DiamondBrown DiamondPink DiamondYellow Diamond

Key Differentiators

• Adamantine luster
• High dispersion (fire)
• Hardness of 10
• Thermal conductivity

Natural vs. Synthetic

Synthetic diamond is commercially available (HPHT (High Pressure High Temperature), CVD (Chemical Vapor Deposition)). Distinguishing natural from synthetic typically requires microscopic examination of internal features.

• UV Fluorescence + Phosphorescence: Variable LW fluorescence (inert to strong blue most common). Pattern angular or irregular. Phosphorescence rare, very weak, < 2 seconds. Synthetic: HPHT: strong chalky blue/green/yellow/orange LW fluorescence with cruciform or hourglass sectoral pattern. Moderate-to-strong phosphorescence (blue/green/orange) lasting many seconds — diagnostically useful. CVD: weak to moderate orange/red/purplish-red fluorescence, patchy or layered pattern. No phosphorescence or extremely brief.
• Polariscope (strain/ADR): Irregular, mottled, chaotic cross-hatch ADR. Not patterned. Synthetic: HPHT: very low to no strain. CVD: 'tatami mat' or 'parquet floor' cross-hatch strain — organized parallel/wavy bands. Diagnostically useful for CVD.
• Microscopy + magnet: Natural inclusions: mineral crystals (garnet, olivine, diopside), feathers, clouds, needles. No metallic inclusions. Synthetic: HPHT: metallic inclusions (dark, opaque, reflective, sometimes with stress halos) — attracted to strong neodymium magnet. CVD: fine pinpoints, diffuse clouds, sometimes linear graphitic inclusions. Both lack typical natural inclusions.
• Lab equipment note: RI/SG identical for all diamond types. Cannot separate origin with standard tools alone. Check the girdle under 10× magnification for laser inscriptions — lab-grown diamonds are often inscribed with 'LGD', the grower's name, or a lab report number. Synthetic: Definitive confirmation requires specialized instruments: DiamondView (De Beers) — UV photoluminescence imaging reveals growth pattern (cuboctahedral for HPHT, layered for CVD); iD100 (Gemological Institute of America) — portable screening device for colorless melee, flags potential synthetics; D-Screen (HRD Antwerp) — automated screening for colorless and near-colorless stones. FTIR (nitrogen type) and Raman spectroscopy also used in lab settings. Refer all high-value stones to an accredited lab.

Common Simulants

• Moissanite: Doubly refractive — facet doubling clearly visible under 10x loupe; thermal probe may not differentiate; use moissanite tester (electrical conductivity) or loupe test.
• Cubic Zirconia (CZ): Very high SG (5.6–6.0) — stone feels heavy; isotropic; thermal probe reads cold; no natural inclusions.
• White Sapphire: Doubly refractive uniaxial negative; RI 1.762–1.778; SG 4.00; appears slightly "fuzzy" face-up vs diamond brilliance.
• White Topaz: Biaxial positive DR; perfect basal cleavage; RI 1.619–1.627; SG 3.53; lower brilliance.
• White zircon: Strong birefringence — facet doubling visible under loupe; very high SG (4.67–4.73); RI 1.925–1.984.

Commonly Confused With

Commonly confused with: Moissanite, Cubic Zirconia, White Sapphire, White Topaz, White Zircon.

Treatments

• Laser Drilling
• Fracture Filling (glass/resin)
• HPHT Color Enhancement
• Irradiation + Annealing (fancy color)
• Surface Coating

Price Context

Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.

Related Comparisons

Diamond Vs Cubic ZirconiaDiamond Vs MoissaniteWhite Sapphire Vs DiamondZircon Vs Diamond

Measurement Guides

How to Identify a GemstoneHow to Measure Specific GravityHow to Use a RefractometerUV Fluorescence Testing