Kyanite
Fazenda do Congonas, Minas Gerais, Brazil

The specimen shown is from Fazenda do Congonas, Minas Gerais, Brazil. The longest crystal measures 44 cm. in length. The specimen was acquired in 1985 from Ann Pizzorusso.



Kyanite     Al2SiO5

Nesosilicates; Aluminum silicate

Color and Luster: Blue, white, colorless, gray, green, nearly black; vitreous; streak colorless

Hardness: Varies: lengthwise 4-5, crosswise 6-7

Cleavage: Perfect, one direction lengthwise; good in a second direction

Fracture: Splintery; transparent to translucent

Crystals: Triclinic; usually in bladed crystal aggregates, less often in terminated crystals

     Kyanite is a common rock forming mineral that shares the same chemical composition with it's two polymorphs silimanite and andalusite. It is the high pressure, triclinic member of the alumino- silicate polymorphs. Kyanite is used in the manufacturing of high temperature, acid resistant ceramics and electrical insulators.

Photo by Lance Kearns


Descriptions taken from
The Audubon Society Field Guide to North American Rocks and Minerals