Lab-Grown Gem Property Table
Grown, not found · Field guide
ReferenceTypical published values. Ranges vary with dopant, composition and measurement wavelength, and a leading ≈ marks figures that are approximate or thinly published — treat those as a starting point rather than a specification.
Want it sorted by refractive index, lowest to highest, with links to what we stock? That is the refractive index list: 40 materials, RI and birefringence only.
Physical and optical properties
| Material | Formula | System | Mohs | Refractive index | Birefringence | Dispersion | SG | Natural analog |
|---|---|---|---|---|---|---|---|---|
| Diamond | C | Cubic | 10 | 2.417 | none | 0.044 | 3.52 | Direct twin |
| Moissanite (SiC) | SiC | Hexagonal (4H / 6H) | 9.25 | 2.648–2.691 | 0.043 | 0.104 | 3.21 | Rare echo |
| Corundum | Al₂O₃ | Trigonal | 9 | 1.762–1.770 | 0.008 | 0.018 | 3.99–4.00 | Direct twin |
| Chrysoberyl | BeAl₂O₄ | Orthorhombic | 8.5 | 1.745–1.755 | 0.008–0.010 | 0.015 | 3.73 | Direct twin |
| LuAG | Lu₃Al₅O₁₂ | Cubic | 8.5 | 1.84 | none | ≈0.025 | 6.73 | No natural analog |
| YAP (Pr:YAlO₃) | YAlO₃ | Orthorhombic perovskite | 8.5 | ≈1.92–1.95 | ≈0.01 | ≈0.02 | 5.35 | No natural analog |
| YAG | Y₃Al₅O₁₂ | Cubic | 8–8.5 | 1.833 ±0.010 | none | 0.028 | 4.50–4.60 | No natural analog |
| Cubic zirconia | ZrO₂ (Y- or Ca-stabilized) | Cubic | 8–8.5 | 2.15–2.18 | none | 0.058–0.066 | 5.6–6.0 | Rare echo |
| GAGG | Gd₃Al₂Ga₃O₁₂ | Cubic | ≈8 | ≈1.92 | none | ≈0.03 | ≈6.6 | No natural analog |
| Spinel (Verneuil) | ≈MgO·2.5Al₂O₃ | Cubic, strained | 8 | 1.727–1.730 | anomalous only | 0.020 | 3.63–3.65 | No natural analog |
| Spinel (flux) | MgAl₂O₄ | Cubic | 8 | ≈1.718 | none | 0.020 | 3.58–3.61 | Direct twin |
| Beryl | Be₃Al₂Si₆O₁₈ | Hexagonal | 7.5–8 | 1.564–1.600 | 0.005–0.009 | 0.014 | 2.67–2.78 | Direct twin |
| Nanosital | SiO₂–Al₂O₃ glass-ceramic | None (nanocrystals in glass) | 7 | 1.65–1.70 | none | 0.015 | 3.5–4.0 | No natural analog |
| Quartz | SiO₂ | Trigonal | 7 | 1.544–1.553 | 0.009 | 0.013 | 2.65 | Direct twin |
| GGG | Gd₃Ga₅O₁₂ | Cubic | 6.5–7 | 1.970 (+0.060) | none | 0.045 | 7.05 | No natural analog |
| Rutile | TiO₂ | Tetragonal | 6–6.5 | 2.616–2.903 | 0.287 | 0.280 | 4.25 | Rare echo |
| Lithium niobate | LiNbO₃ | Trigonal | 5–5.5 | 2.21–2.30 | 0.090 | 0.120 | 4.64 | No natural analog |
| Strontium titanate | SrTiO₃ | Cubic | 5–6 | 2.409 | none | 0.190 | 5.13 | Rare echo |
| Bismuth germanate (BGO) | Bi₄Ge₃O₁₂ | Cubic | 5 | 2.15 | none | ≈0.10 | 7.13 | No natural analog |
| KTP | KTiOPO₄ | Orthorhombic | 5 | 1.74–1.83 | ≈0.09 | ≈0.04 | 3.03 | No natural analog |
| YVO₄ | YVO₄ | Tetragonal | ≈5 | 1.99 / 2.22 | ≈0.22 | ≈0.08 | 4.22 | Rare echo |
| Zincite | ZnO | Hexagonal | 4–5 | 2.013–2.029 | 0.016 | 0.127 | 5.68 | Rare echo |
| Fluorite | CaF₂ | Cubic | 4 | 1.434 | none | 0.007 | 3.18 | Direct twin |
Critical angle and why it matters
Total internal reflection only happens beyond the critical angle, and that angle falls as refractive index rises. So leakage runs from high RI to low: a shallow pavilion designed for CZ or rutile will leak in quartz. A steep quartz pavilion won't leak that way in CZ or rutile, but it usually looks darker and less lively than the material should. If you take one number from this page into the workshop, take this one.
| Material | Refractive index | Critical angle |
|---|---|---|
| Fluorite | 1.434 | 44.2° |
| Quartz | 1.544–1.553 | 40.2° |
| Beryl | 1.564–1.600 | 39.4° |
| Nanosital | 1.65–1.70 | 37.3° |
| Spinel (flux) | ≈1.718 | 35.6° |
| Chrysoberyl | 1.745–1.755 | 34.8° |
| Corundum | 1.762–1.770 | 34.5° |
| YAG | 1.833 ±0.010 | 33.1° |
| LuAG | 1.84 | 32.9° |
| GAGG | ≈1.92 | 31.4° |
| YAP (Pr:YAlO₃) | ≈1.92–1.95 | 31.2° |
| GGG | 1.970 (+0.060) | 30.5° |
| Zincite | 2.013–2.029 | 29.7° |
| YVO₄ | 1.99 / 2.22 | 28.4° |
| Cubic zirconia | 2.15–2.18 | 27.5° |
| Lithium niobate | 2.21–2.30 | 26.4° |
| Strontium titanate | 2.409 | 24.5° |
| Diamond | 2.417 | 24.4° |
| Moissanite (SiC) | 2.648–2.691 | 22.0° |
| Rutile | 2.616–2.903 | 21.2° |
The practical rule: higher RI means shallower pavilion angles. Most faceting design libraries specify the RI range a design was optimized for. Using a design outside that range is the most common reason a technically well-cut stone looks dark in the middle.
Growth method and origin
| Material | Grown by | Originally developed for |
|---|---|---|
| Beryl | Flux, hydrothermal | Gems, full stop (Nacken 1920s, IG Farben 1930s) |
| Chrysoberyl | Czochralski, flux, floating zone | Gems (Creative Crystals, 1973), with laser rods developed alongside |
| Corundum | Verneuil, Czochralski, Kyropoulos, flux, hydrothermal, HEM, EFG | Gems and watch bearings — then LED substrates and phone windows |
| Cubic zirconia | Skull melting (cold crucible) | Refractory and laser-host research, Moscow, 1960s–70s |
| Diamond | HPHT press; microwave plasma CVD | Abrasive grit (GE, 1955) |
| Fluorite | Bridgman–Stockbarger | Deep-UV lithography lenses and infrared windows |
| GAGG | Czochralski | Fast scintillator for medical and security imaging |
| GGG | Czochralski | Substrate for magnetic bubble memory |
| Lithium niobate | Czochralski | Optical modulators and the SAW filters in most phones |
| LuAG | Czochralski, Bridgman | Scintillator for medical imaging and particle detectors |
| Moissanite (SiC) | Physical vapor transport | Abrasive, then LED and power-electronics wafers |
| Nanosital | Melt, then controlled crystallization | Engineering glass-ceramics (cookware, radomes, mirror blanks) |
| Quartz | Hydrothermal | Piezoelectric oscillators for radio and electronics |
| Rutile | Verneuil, then oxygen anneal | Pigment research at National Lead, with a cut gem as a stated goal |
| Spinel (flux) | Flux, Czochralski, Verneuil (off-composition) | An accident while chasing cobalt-blue sapphire |
| Strontium titanate | Verneuil | Physical-property research at National Lead; sold as a diamond simulant from about 1955 |
| YAG | Czochralski | Nd:YAG laser host (Bell Labs, 1964) |
| YAP (Pr:YAlO₃) | Czochralski | Laser host and fast scintillator |
| YVO₄ | Czochralski | Optical isolators for fiber telecom; Nd:YVO₄ laser host |
| Zincite | Accidental vapor deposition in smelter flues | Nothing — it was industrial waste |
Grown, not found: the field guide
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Reference
A reference to lab-grown gem materials, written for cutters. Values are typical published figures; ranges vary with composition, dopant and measurement wavelength. Nothing here is a substitute for a laboratory report on a stone whose identity matters commercially.