Mineral Species: Andalusite

Chemical Formula: Al2SiO5

Chemical Name: Aluminium Silicate

Mineral Class: Nesosilicate

Mineral Notes: Andalusite is a polymorph with two other aluminium silicates, Kyanite and Sillimanite. A polymorph is a mineral that shares the same chemistry but a different crystal structure with another, or other, minerals. An unusual variety of Andalusite is called "Chiastolite". It contains black or brown clay and/or carbonaceous material inclusioned in the crystal. These inclusions are arranged in regular symmetrical shapes. Usually they are in the form of a cross or X. 

Description: A rosette of elongated Andalusite crystals upon a matrix of Quartzite. The mineral has a pale purple colour and has a very distinct vitrous luster. Many of the crystals have the appearance of flattend blades and on some the end terminations can easily be seen.

Location: Dolni Bory, Czech Republic.