Diamond Specialist Certification Course
Properties of Diamond Simulants
Purchase Diamond Specialist Certification CourseLearn the fundamentals of diamonds — from optical and physical properties to grading and ethical and legal issues. Learn to distinguish natural diamonds from synthetics and diamond simulants. Keep the kit, which includes one natural, jewelry-grade diamond. If you successfully pass the quiz and gem identification test, then you will be an IGS-certified Diamond Specialist.
This information, in conjunction with our article on distinguishing diamonds, can help you separate diamonds from their imitators.
Identifying Synthetic Diamonds
Until relatively recently, gem-grade synthetic diamonds rarely appeared in jewelry. This is changing. Consult our article on identifying synthetic diamonds for advice on distinguishing natural or mined diamonds from their lab-created counterparts.
Properties of Natural Diamonds vs. Diamond Simulants
|Properties||Natural Diamond Type Ia||Natural Diamond Type Ib||Natural Diamond Type IIa||Natural Diamond Type IIb||Moissanite||Cubic Zirconia|
|RI||2.417||2.417||2.417||2.417||2.648 - 2.691||2.15 - 2.18|
|Dispersion||.044||.044||.044||.044||.009 - .104||.058 - .066|
|Optic Character||Isotropic||Isotropic||Isotropic||Isotropic||Uniaxial +||Isotropic|
|SG||3.515||3.515||3.515||3.515||3.17 - 3.22||5.56 - 6.00|
|Hardness||10||10||10||10||9 ¼||8 - 8 ½|
|Cleavage||Perfect, four directions||Perfect, four directions||Perfect, four directions||Perfect, four directions||None||None|
|Absorption Spectra||Dark line at 415 and 478 nm, often more||Increasing absorption towards blue end||Variable, usually 504||Variable||No sharp bands, strong absorption below 425||Not diagnostic|
|UV||Colorless stones, inert to strong, usually blue (LW) Weaker (SW)||Variable, can be inert, usually blue or yellow||Variable, can be inert, often red||Inert but phosphoresce after exposure to SW UV||Brownish yellow, (LW)||Greenish/yellow or orangish/yellow (LW) Yellow (SW) Colored CZ varies|
|Girdle Surface||Waxy, polished or granular||Waxy, polished or granular||Waxy, polished or granular||Waxy, polished or granular||Frosted, polished or striated||Frosted or polished|
|Facet Junctions||Sharp||Sharp||Sharp||Sharp||Sharp or slightly rounded||Sharp or slightly rounded|
|Electrical Test||None||None||Very Weak||Strong||Frequent, variable intensity||None|
|Inclusions||Bearding, crystals, planar graining||Bearding, crystals, planar graining||Bearding, crystals, planar graining||Bearding, crystals, planar graining||Bearding, crystals, planar graining||Gas bubbles, negative crystals, unmelted powder|
|Properties||GGG||YAG||Synthetic Spinel*||White Sapphire||White Topaz||Glass|
|RI||1.970 - 2.03||1.823 - 1.843||1.720 - 1.740||1.757 - 1.779||1.609 - 1.637||1.40 - 1.70|
|Birefringence||None||None||None||.008 - .010||.008 - .010||None|
|Dispersion||.038 - .045||.028||.020||.018||.014||.009 - .098|
|Optic Character||Isotropic||Isotropic||Isotropic||Uniaxial -||Biaxial +||Amorphous|
|Pleochroism||None||None||None||None if totally colorless||None if totally colorless||None|
|Luster||Vitreous to subadamantine||Vitreous to subadamantine||Vitreous to subadamantine||Vitreous to subadamantine||Vitreous||Vitreous|
|SG||7.01 - 7.15||4.50 - 4.60||3.52 - 3.67||3.90 - 4.10||3.49 - 3.57||2.30 - 4.50|
|Hardness||6.5 - 7||8.25 - 8.5||7.5 - 8||9||8||5 - 6|
|Cleavage||None||None||None||None||Perfect, 1 direction||None|
|Absorption Spectra||Not diagnostic||Not diagnostic||Not diagnostic||Not diagnostic||Not diagnostic||Not diagnostic|
|UV||Moderate to strong, pinkish orange (SW)||Inert to moderate orange, (LW) Inert to weak orange, (SW)||Occasionally, weak green (LW) Moderate to strong chalky or greenish blue, (SW)||Natural: Inert to moderate red to orange (LW & SW)Synthetic: inert to weak, blueish white (SW)||Not diagnostic||Not diagnostic|
|Girdle Surface||Frosted or polished||Frosted or polished||Frosted or polished||Frosted or polished||Frosted or polished||Frosted or polished|
|Facet Junctions||Slightly rounded||Sharp or slightly rounded||Sharp or slightly rounded||Sharp or slightly rounded||Sharp or slightly rounded||Rounded|
|Inclusions||Gas bubbles||Gas bubbles, curved striae||Gas bubbles||Natural: Silk, crystals, fingerprint, hexagonal banding. Synthetic: bubbles, curved striae, flux||2 & 3 phase||Bubbles, swirl lines, concave facets|
Compliments of the International Gem Society.
* Colorless natural spinels are extremely rare. Should you encounter a colorless spinel as a diamond simulant, it's very likely synthetic.
For information on diamond color treatments, see our article on HPHT diamonds.
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