Mica

Real mineral · common · KAl₂(AlSi₃O₁₀)(OH)₂

A group of sheet silicates with perfect basal cleavage yielding flexible, transparent flakes. Forms in granites, pegmatites, and metamorphic schists. Its reflective flakes account for the sparkle in many metamorphic rocks.

Identity

Formula

KAl₂(AlSi₃O₁₀)(OH)₂

Chemical class

silicate

Also known as

Muscovite (white mica), Biotite (black mica), Lepidolite (lilac), Phlogopite

Crystallography

Crystal system

monoclinic

Habits

foliated, tabular, massive

Fracture

uneven

Physical properties

Mohs hardness

2.5

Density

2.83 g/cm³

Luster

pearly, vitreous

Colors

colorless, white, gray, brown, green, black

Streak

white

Transparency

transparent, translucent

Geology

Origins

igneous, metamorphic

Host rocks

granite, schist, gneiss, pegmatite

Associated minerals

Quartz, feldspar, Tourmaline, Garnet

Geography

worldwide

Classification

Rarity

common

Gem quality

No

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