Andalusite
JewelryWiki Editorial·3 sources·Reviewed 2026-08-04
Strongly pleochroic — it shows different colours down different crystal axes, so a cut stone can flash green and red as it turns.
Properties
| Property | Value | Authority |
|---|---|---|
| Mohs hardness | 7½ [1] | — |
| Refractive index | 1.627–1.649 [1] | — |
| Specific gravity | 3.05–3.20 [1] | — |
| Chemical formula | Al2SiO5 [3] | — |
| Crystal system | Orthorhombic [2] | — |
Sources
- International Gem Society — reference charts (Mohs hardness, specific gravity, refractive index) — International Gem Society (IGS reference charts)
- Wikipedia — mineral article infoboxes (crystal system) — Wikipedia contributors (Wikipedia mineral infoboxes)
- Handbook of Mineralogy — Mineral Data Publishing / Mineralogical Society of America (Handbook of Mineralogy, Mineral Data Publishing)