Brief Description: Its name originates from the area Labrador of Canada, where it was found. Labradorite belongs to the Tectosilicates category (Plagioclase). Plagioclases are isomorphic mixtures between the opposite members albite NaAlSi3O8 (Ab) and anorthite CaAl2Si2O8 (An). The plagioclases that have less than 50% anorthite (An) are called acidic and those that have more than 50% An are called basic. Labradorite contains An 50-70 and, therefore, belongs to the basic Plagioclases. The lustre of Plagioclases is vitreous or pearly. The colour ranges from colourless, white or grey. It can also be bluish, greenish or incarnadine. In the case of Labradorite, nice colour (blue, green) interplay is often observed. They have specific gravity 2.6 ? 2.8 and they are transparent to semitransparent. Their hardness is 6 and their fusibility 4 ? 4.5. The crystals of the plagioclases are usually tabular. They are often found in irregular grains and schistose masses and alter into kaolinite and sericite. Acidic plagioclases are tougher in alteration than basic plagioclases and transform in a mixture of zoisite, calcite, sericite and albite. They are of the widest spread petrogenetic minerals and occur in igneous and transformed rocks. Labradorite is used as ornamental material due to the nice alteration of its colours. 
Bibliography: Ευρετήριο ορυκτών ΑΠΘ στην ιστοσελίδα http://www.geo.auth.gr/106/az_gr.htm Τσιραμπίδης Α. (2005). Ο ορυκτός πλούτος της Ελλάδας. Εκδόσεις Γιαχούδη Θεσσαλονίκη, σελ. 391.