Diamond and Simulant Comparison Chart
Compliments of
The International Gem Society
| Properties | Natural Diamond Type Ia | Natural Diamond Type Ib | Natural Diamond Type IIa | Natural Diamond Type IIb | Moissanite | Cubic Zirconium |
|---|---|---|---|---|---|---|
| RI | 2.417 | 2.417 | 2.417 | 2.417 | 2.648 - 2.691 | 2.15 - 2.18 |
| Birefringence | None | None | None | None | .043 | None |
| Dispersion | .044 | .044 | .044 | .044 | .009 - .104 | .058 - .066 |
| Optic Character | Isotropic | Isotropic | Isotropic | Isotropic | Uniaxial + | Isotropic |
| Pleochroism | None | None | None | None | None | None |
| Read Through | None | None | None | None | None | Slight |
| Luster | Adamantine | Adamantine | Adamantine | Adamantine | Adamantine | Subadamantine |
| 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 5040 | 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 |
| Thermal Test | "Diamond" | "Diamond" | "Diamond" | "Diamond" | "Diamond" | "Simulant" |
| 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 Sapphires | 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 |
| Read Through | Moderate | Strong | Strong | Strong | Strong | Strong |
| 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, bluish 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 |
| Electrical Test | None | None | None | None | None | None |
| Thermal Test | "Simulant" | "Simulant" | "Simulant" | "Simulant" | "Simulant" | "Simulant" |
| 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 |