Mineral Type - Kyanite

Common metamorphic silicate mineral. The generally bluish colour is caused by Fe(II)-Fe(III) charge transfer (Faye and Nickel, 1969).

Name

Named in 1789 by Abraham Gottlieb Werner from the Greek word "kyanos", meaning "blue," the common colour of the species. The French spelling, "Cyanite", was commonly used by mineralogists through much of the 19th and early 20th centuries.

Physical Properties

Lustre: Vitreous, Sub-Vitreous, Greasy, Pearly
Transparency: Transparent, Translucent. Somewhat pearly on {100} || to the perfect cleavage
Colour: Blue, white, light grey, green, rarely yellow, orange, pink
Streak: Colourless
Hardness: 5½ - 7 on Mohs scale. 5.5 parallel to [001], 7 parallel to [100]
Tenacity: Brittle
Cleavage: Perfect. Perfect on (100), good on (010)
Parting; On (001)
Fracture: Splintery
Density: 3.53 - 3.67 g/cm3 (Measured) 3.67 g/cm3 (Calculated)

Chemical Properties

Formula: Al2(SiO4)O
Elements listed: Al, O, Si

Crystallography

Crystal System: Triclinic
Class (H-M): 1 - Pinacoidal
Space Group: P1
Morphology: Crystals bladed or tabular
Twinning: Lamellar on (100), common

Synonyms

Cyanite, Distene, and Disthene

Varieties

Rhätizite