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Natural AlexandriteVSAndalusite
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 Andalusite, 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: Andalusite | Verdict |
|---|---|---|---|
| Refractive index (RI) | 1.745–1.755 | 1.629–1.650 | A higher |
| Specific gravity (SG) | 3.71–3.75 | 3.13–3.21 | A higher |
| Mohs hardness | 8.5 | 7.0–7.5 | A higher |
| Birefringence | 0.009 | 0.011 | B higher |
| Dispersion | — | — | — |
| Property | A: Natural Alexandrite | B: Andalusite |
|---|---|---|
| Crystal system | 斜方晶系 | 斜方晶系 |
| Pleochroism | 強（緑・赤紫・黄橙） | 強（緑・赤・黄） |
| Chelsea filter | red | inert |
| UV (long-wave) | weak (red) | inert |
| UV (short-wave) | weak (red) | inert |
◆Alexandrite shows a color change between daylight and incandescent illumination (emerald-to-ruby) but the same color in both views from any given angle; andalusite shows three different colors in a single lighting condition depending on viewing angle through the crystal.
Distinguishing tools
Tools that decide between Natural Alexandrite and Andalusite in practice.
- High-output penlightDETAILS →
Switch between daylight and warm incandescent light to verify color change
- Chelsea filterDETAILS →
Quick chrome-content screen — chromium-bearing stones glow red through the filter
- Handheld spectroscopeDETAILS →
Absorption-line pattern identifies the chromophore (Cr, Fe, or Co)
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.