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Natural AlexandriteVSSynthetic Color-Change Sapphire (Vanadium-Doped Corundum)
Side-by-side comparison of physical properties, fluorescence, and crystal system — to identify by observation.
- ◎ is higher in Synthetic Color-Change Sapphire (Vanadium-Doped Corundum), giving a numerical distinguishing point.
- ◎ is higher in Synthetic Color-Change Sapphire (Vanadium-Doped Corundum), giving a numerical distinguishing point.
- ◎ is higher in Synthetic Color-Change Sapphire (Vanadium-Doped Corundum), giving a numerical distinguishing point.
- ◎ is higher in Natural Alexandrite, giving a numerical distinguishing point.
Note: properties whose numeric ranges do not overlap are auto-extracted. Both are measurable with a refractometer or heavy-liquid bath.
| Property | A: Natural Alexandrite | B: Synthetic Color-Change Sapphire (Vanadium-Doped Corundum) | Verdict |
|---|---|---|---|
| Refractive index (RI) | 1.745–1.755 | 1.762–1.770 | B higher |
| Specific gravity (SG) | 3.71–3.75 | 3.98–4.05 | B higher |
| Mohs hardness | 8.5 | 9.0 | B higher |
| Birefringence | 0.009 | 0.008 | A higher |
| Dispersion | — | — | — |
| Property | A: Natural Alexandrite | B: Synthetic Color-Change Sapphire (Vanadium-Doped Corundum) |
|---|---|---|
| Crystal system | 斜方晶系 | 六方晶系（三方晶系） |
| Pleochroism | 強（緑・赤紫・黄橙） | 強（変色性に対応） |
| Chelsea filter | red | — |
| UV (long-wave) | weak (red) | — |
| UV (short-wave) | weak (red) | weak (green) |
◆Natural alexandrite is BeAl₂O₄ : Cr (chrysoberyl) with RI 1.741–1.760, SG 3.68–3.78, Mohs 8.5, and a chromium-driven green-red color shift — fundamentally a different species. Synthetic color-change sapphire is vanadium-doped corundum (Al₂O₃ : V) with RI 1.762–1.770, SG 4.00, Mohs 9, and a vanadium-driven blue-purple shift. Species verification at a major lab takes minutes and definitively separates them.
Distinguishing tools
Tools that decide between Natural Alexandrite and Synthetic Color-Change Sapphire (Vanadium-Doped Corundum) in practice.
Note: this page is auto-generated from published GIA / CGL reference values. Individual stones, treatments, and synthetics may fall outside these ranges. For a definitive identification, consult an accredited gem laboratory.