Andalusite
Andalusite is named after Andalucia, the region in Spain where it was first discovered. It is well known for its strong pleochroism, being very strong in the green and reddish-brown material. Flashes of red, yellow and olive green may be seen at the same time in faceted stones, revealing an attractive display of trichroic pleochroism. The material can be transparent to opaque.
Source locations for Andalusite include: Australia, Brazil, Canada, Russia, Spain (Andalucia), Sri Lanka and France.
Andalusite was little known about, but more is appearing on the market as it's attributes are being realised.
Properties of the Gemstone and Additional Information
| Gemstone type: | Andalusite |
| Crystal System: | Orthorhombic |
| Chemical Composition: | Aluminium silicate, Al2SiO5 |
| Colour: | Yellow-green, green, brownish-red |
| Lustre: | Vitreous |
| Pleochroism: | Trichroic strong: colours seen as yellowish-green, green, reddish-brown to dark red. |
| Dispersion: | Low |
| Hardness: | 7 1/2 on the Mohs' scale. |
| Toughness: | Good, even though it has good cleavage. |
| Cleavage: | Good |
| Density in gm/cc: | 3.15 to 3.20 |
| Double refraction: | Yes |
| Refractive index: | 1.63 to 1.64 |
Common Treatments
Andalusite is not normally treated.