Mineral Species: Microcline

Chemical Formula: KAlSi3O8

Chemical Name: Potassium Aluminum Silicate

Mineral Class: Tectosilicate

Mineral Notes: Microcline is a common mineral often used as a semi-precious stone under the names of Amazonite and Perthite. Microcline is a polymorph with several other minerals that share the same chemistry but have different crystal structures. Twinning is very common, giving rise to several different forms depending on the level and angle of interpenetration. Microcline is a diamorph of Orthoclase. It is named from the Greek words mikron (little) and klinein (to stoop). 

Description: Large blocky crystal of green Amazonite. The colour is particulalry attractive and the mineral has a strong glassy luster. There is considerable surface refraction of light at the ends of the crystal, producing numerous sub-surface reflections and sheens.

Location: Santa Maria de Itabira Mine, Minas Gerais, Brazil.