Andalusite

Andalusite: polymorph of Aluminum Silicate (Al₂SiO₅) (the other forms are Sillimanite and Kyanite), crystallizing in the Orthorhombic System, occurring as prismatic crystals with a square cross-section, as well as in masses and fibrous aggregates; colors range from pink, reddish-brown, to green with strong pleochroism; density 3.15–3.17 g/cm³; Mohs hardness 6.5–7.5; refractive indices 1.632–1.638–1.643.

back to the gemological glossary