Blades of Kyanite in Quartz. Picture
field of view is 3.5 inches.
Kyanite in Fuschite from the Cola Peninsula, Russia. Center crystal is 1"
long.
Kyanite from Squaw Peak, Arizona. Specimen is 2.5" across. Close-up
on right.
Dark gray Kyanite from Morocco.
CHEMISTRY Al2SiO5 Aluminum silicate
CRYSTALLOGRAPHY Triclinic
CRYSTAL GROWTH AND HABITS Crystals of Kyanite are very commonly bladed, sometimes twisted or bent. It is also tabular.
COLOR AND OTHER OPTICAL PROPERTIES Kyanite is usually blue but can be white, and rarely green or yellowish gray to black.
HARDNESS 5 in the long dimension of the blades and 7 across the blades
SPECIFIC GRAVITY 3.5 - 3.7
LUSTER Vitreous to pearly
STREAK White
BREAKABILITY Near perfect cleavage in 1 direction and good in another producing an angle of 79o. Its fracture is splintery.
OCCURRENCE Kyanite is typically found in gneisses or granitic pegmatites and in quartz veins. It is also produced by the moderately high pressures associated with regional metamorphism of pelitic sediments.
ASSOCIATED MINERALS Staurolite, Andalusite, Sillimanite, Talc, Corundum