metamorphic
Talc
Talc (Hydrated magnesium silicate, Mg3Si4O10(OH)2)
Hardness: 1 on Mohs scale (can be scratched by a fingernail). Color: White, pale green, or gray. Luster: Pearly to greasy. Crystal System: Monoclinic. Feel: Distinctly soapy or greasy touch. Cleavage: Perfect basal cleavage.
- Hardness
- 1 on Mohs scale (can be scratched by a fingernail)
- Color
- White, pale green, or gray
- Luster
- Pearly to greasy
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Physical properties
Hardness: 1 on Mohs scale (can be scratched by a fingernail). Color: White, pale green, or gray. Luster: Pearly to greasy. Crystal System: Monoclinic. Feel: Distinctly soapy or greasy touch. Cleavage: Perfect basal cleavage.
Formation & geological history
Formed primarily by the metamorphism of magnesian minerals such as pyroxene, amphibole, and olivine in the presence of carbon dioxide and water. Common in metamorphic belts containing ultramafic rocks.
Uses & applications
Used extensively in the manufacture of paper, paints, plastics, ceramics, rubber, and cosmetics (talcum powder). It is also used as a lubricant and in sculpture under the name 'soapstone'.
Geological facts
Talc is the softest known mineral on Earth and defines the value of 1 on the Mohs scale of mineral hardness. It has been used for thousands of years by various cultures for carving ornaments and cooking vessels due to its softness and heat resistance.
Field identification & locations
Identified in the field by its extreme softness and characteristic soapy feel. It is commonly found in metamorphic terranes in regions like the Appalachian Mountains, the Alps, and the Himalayas.
