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Natural AlexandriteVSAndesine-Labradorite
Side-by-side comparison of physical properties, fluorescence, and crystal system — to identify by observation.
- ◎ is higher in Natural Alexandrite, giving a numerical distinguishing point.
- ◎ is higher in Natural Alexandrite, giving a numerical distinguishing point.
- ◎ is higher in Natural Alexandrite, 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: Andesine-Labradorite | Verdict |
|---|---|---|---|
| Refractive index (RI) | 1.745–1.755 | 1.543–1.573 | A higher |
| Specific gravity (SG) | 3.71–3.75 | 2.65–2.74 | A higher |
| Mohs hardness | 8.5 | 6.0–6.5 | A higher |
| Birefringence | 0.009 | 0.008 | A higher |
| Dispersion | — | — | — |
| Property | A: Natural Alexandrite | B: Andesine-Labradorite |
|---|---|---|
| Crystal system | 斜方晶系 | 三斜晶系 |
| Pleochroism | 強（緑・赤紫・黄橙） | 弱い多色性 |
| Chelsea filter | red | — |
| UV (long-wave) | weak (red) | — |
| UV (short-wave) | weak (red) | inert |
◆Alexandrite (BeAl₂O₄ chrysoberyl, Mohs 8.5, SG 3.70–3.75, RI 1.746–1.755, doubly refractive biaxial positive, dramatic three-axis , dramatic green-to-red colour change) versus andesine-labradorite (plagioclase feldspar, Mohs 6–6.5, SG 2.65–2.74, RI 1.543–1.573, doubly refractive biaxial, weak-to-medium , moderate colour change). The refractive-index and specific-gravity differences are dramatic and diagnostic — no possible confusion on a refractometer or hydrostatic balance. The colour-change character differs: alexandrite's classical 'emerald by day, ruby by night' green-to-red shift versus andesine-labradorite's red-to-cherry shift. The hardness difference (Mohs 8.5 versus 6–6.5) is decisive. The plagioclase-feldspar twinning lamellae and the two perfect directions are diagnostic of feldspar; alexandrite shows neither. The 'Tibet andesine' 2003–2011 controversy specifically marketed diffusion-treated material as an alexandrite-substitute at lower price tier, which was the commercial driver of the fraud; the 2008–2011 investigation closed the supply-illusion.
Distinguishing tools
Tools that decide between Natural Alexandrite and Andesine-Labradorite 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.