Talc
Species
Common · Mg₃Si₄O₁₀(OH)₂
The softest mineral on the Mohs scale. Forms when hot fluids alter serpentinised mafic and ultramafic rocks, and when siliceous dolomites are metamorphosed at low temperature. 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 (talc-rich rock), Steatite (massive talc)
Crystallography
- Crystal system
- Monoclinic
- Habits
- Foliated, Massive, Granular
- Fracture
- Fibrous
Physical properties
- Mohs hardness
- 1
- Density
- 2.75 g/cm³
- Luster
- Pearly, Waxy, Dull
- Colors
- white, gray, green, brown
- Streak
- white
- Transparency
- Transparent, Translucent
Geology
- Origins
- Metamorphic, Hydrothermal
- Host rocks
- Ultramafic rock (peridotite, serpentinite), Schist and gneiss, Limestone and chalk
- Associated minerals
- Serpentine, Chlorite, Calcite, Tremolite
- Found in
- Garnierite, Schist, Soapstone
- Geography
- France (Trimouns, Luzenac), Austria (Tyrol), Switzerland (Valais, Ticino), Italy, Norway, Russia (Irkutsk), USA (Vermont, New York)
Classification
- Rarity
- Common
- Gem quality
- No
Sources
- M. Pasero and others, IMA Commission on New Minerals, Nomenclature and Classification, The New IMA List of Minerals, updated September 2026. International Mineralogical Association (CNMNC), 2026.
- Talc. Mindat.org (Hudson Institute of Mineralogy).
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Talc. Mineral Data Publishing, Handbook of Mineralogy, 2001.
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