Kyanite

Real mineral · uncommon · Al₂SiO₅

Aluminium silicate formed under high-pressure metamorphic conditions. Unusual in having two different hardnesses: 5.5 along the crystal length and 7 across it. Used as an indicator mineral to estimate the pressure of metamorphism.

Identity

Formula

Al₂SiO₅

Chemical class

silicate

Also known as

Cyanite, Disthene

Crystallography

Crystal system

triclinic

Habits

tabular, prismatic, fibrous

Fracture

splintery

Physical properties

Mohs hardness

5.5

Density

3.67 g/cm³

Luster

vitreous, pearly

Colors

blue, pale blue, white, gray, green, black

Streak

white

Transparency

transparent, translucent

Geology

Origins

metamorphic

Host rocks

schist, gneiss, quartzite

Associated minerals

Quartz, Staurolite, Garnet, Mica

Geography

Brazil, USA, Kenya, India, Austria

Classification

Rarity

uncommon

Gem quality

Yes

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