Andalusite

Andalusite gemstones are remarkable for their fascinating color habits and very strong pleochroism, which can cause a muliticolored effect of shades of yellow, olive-green, and reddish-brown within a single gem. Although Andalusite as a mineral is not uncommon, the transparent variety used as a gem is very rare. Another important form of Andalusite that is entirely different is the mostly opaque Chiastolite variety, which is known for its unique cross-shaped design within the body of a crystal.
Chemical Formula Al2SiO5
Color White, Green, Yellow, Orange, Brown, Pink, Gray, Black, Multicolored
Hardness 7Â -Â 7.5
Crystal System Orthorhombic
Refractive Index 1.62Â -Â 1.65
SG 3.1Â -Â 3.2
Transparency Transparent to opaque
Double Refraction -0.01
Luster Vitreous
Cleavage 2,1
Mineral Class Andalusite