Andalusite

The variety chiastolite commonly contains dark inclusions of carbon or clay which form a checker-board pattern when shown in cross-section.
The clear variety first found in Andalusia, Spain can be cut into an interesting gemstone.^[Faceted andalusite stones give a play of red, green, and yellow colours that resembles a muted form of iridescence, although the colours are actually the result of unusually strong pleochroism.

Location - Andalusia, Spain

Group - Silica

R.I - 1.633 - 1.644

Hardness - 6.5 - 7.5

Andalusite