Brief Description: Its name derives from its blue colour. The name disthene derives from the Greek words dyo (two) and sthenos (valence), because it has two different hardnesses depending on the crystal's orientation. Its chemical formula is Al2SiO5 and it belongs to the category Aluminium Silicates. Its lustre is vitreous or pearly, usually with blue colour with darker shades in the centre of the crystal. Additionally, white, ashy or yellow. The colour is often in irregular regions. Its specific gravity is 3.6. Its hardness is 5 parallel and 7 vertically on the crystal?s elongation. It is a transparent to semitransparent mineral and does not fuse. It crystallizes in the triclinic system and is found in blade-like or tabular crystals, in scattered oblong crystals or blade-like, columnar aggregations. It changes into sericite and kaolinite. It transforms into two other polymorphic (sillimanite, andalusite). It is a typical mineral of aluming rocks general transformation and indicator of deep transformation. It often connects with granate, staurolite and corundum. It often occurs in eclogites. It is used in the manufacture of very difficult to melt porcelain. 
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. Berry, L.G., Mason, B. and Dietrich, R.V. (1983). Mineralogy. W. H. Freeman and Company, San Francisco, 561 pp. Σαπουντζής, Η. και Χριστοφίδης, Γ. (1985). Ορυκτοδιαγνωστική. University Studio Press, Θεσσαλονίκη, 241 σ.