Talc

Real mineral · common · Mg₃Si₄O₁₀(OH)₂

The softest mineral on the Mohs scale. Forms by hydrothermal alteration of olivine and pyroxene in ultramafic rocks. Its greasy feel results from a layer structure in which sheets slide easily over one another.

Identity

Formula

Mg₃Si₄O₁₀(OH)₂

Chemical class

silicate

Also known as

Soapstone (massive variety), Steatite

Crystallography

Crystal system

monoclinic

Habits

foliated, massive, granular

Fracture

uneven

Physical properties

Mohs hardness

1

Density

2.75 g/cm³

Luster

pearly, waxy, dull

Colors

white, gray, green, brown

Streak

white

Transparency

translucent, opaque

Geology

Origins

metamorphic, hydrothermal

Host rocks

serpentinite, dolomite, schist

Associated minerals

Serpentine, Chlorite, Calcite, Tremolite

Geography

China, India, Brazil, USA, Finland

Classification

Rarity

common

Gem quality

No

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