Kyanite

Kyanite is a typically blue aluminosilicate mineral found in aluminium-rich metamorphic pegmatites and sedimentary rock. It is the high-pressure polymorph of andalusite and sillimanite, so the presence of kyanite in metamorphic rocks generally indicates metamorphism deep in the Earth's crust. It is strongly anisotropic, its hardness varying with crystallographic direction, which together with its blue color is an identifying characteristic, and its name derives from the Ancient Greek word for dark blue. It is used as a raw material in the manufacture of ceramics and abrasives. In this atlas it is the mineral species that the gemstone kyanite records.