Home Minerals Talc

Talc

Talc is easily distinguishable by its extreme softness, color is white, colorless, pale to dark green, or yellowish to brown. Crystals are rare; it is most commonly found in foliated, fibrous, or massive aggregates. It is often found mixed with other minerals, such as serpentine and calcite. Dense, high-purity talc is called steatite. It is a metamorphic mineral found in veins and magnesium-rich rocks. It is often associated with serpentine, tremolite and forsterite and occurs as an alteration product of silica-poor igneous rocks. Talc is widespread and is found in most areas of the world where low-grade metamorphism occurs. The name soapstone is given to compact masses of talc and other minerals due to their soapy or greasy feel.

Association: Actinolite, tremolite, chlorite, pyroxene, vermiculite, serpentine, anthophyllite, dolomite, calcite.

Chemical Properties

Chemical Classification Silicate mineral
Chemical Composition Mg3Si4O10(OH)2

Physical Properties of Talc

Color White, beige, gray, yellow, brown, pink, purple, blue, green. Rarely colorless.
Streak White
Luster Greasy, waxy, pearly
Diaphaneity Translucent
Mohs Hardness 1
Specific Gravity 2.7 to 2.8
Diagnostic Properties Feel, color, softness, cleavage
Crystal System Triclinic or monoclinic.
Tenacity Sectile
Fracture Fibrous, Micaceous
Density 2.58 – 2.83 g/cm3 (Measured)    2.78 g/cm3 (Calculated)

Optical Properties of Talc

Cleavage Perfect on {001}
Color / Pleochroism Weak in dark varieties
Optic Sign Biaxial (-)
Birefringence δ = 0.051
Relief Moderate

Occurrence

In talc-rich schists or steatite through hydrothermal alteration of ma¯c rocks (steatitization) subsequent to serpentinization during greenschist facies metamorphism. Also formed by thermal low-temperature metamorphism of siliceous dolostones.

Talc Uses

Talc has many uses.

  • In the making of paper, paint, plastic, electrik, food, medicine, cosmetics and ceramics
  • Due to its resistance to heat, electricity and acids, it is used on laboratory tabletop surfaces and surfaces of power plants.
  • Talc is used as cosmetic (talcum powder), as a lubricant and as a filler in paper production.
  • It is used to cover the inner parts of the inner tubes and rubber gloves during production to prevent the surfaces from sticking.
  • In medicine, talc is used as a pleurodesis agent to prevent recurrent pleural effusion or pneumothorax. In the European Union, the contribution number is E553b.
  • The talc can be used as a polishing agent in the polishing stage in the white rice process.
  • It is widely used in the ceramic industry both in the body and in the secrets. Low-fire artwork gives whiteness to its bodies and increases thermal expansion against crushing.

Distribution

Of widespread occurrence. Some localities for good crystals or pure material include:

  • on Mt. Greiner, Zillertal, Tirol, Austria.
  • At Zermatt, Valais, and St. Gotthard, Ticino, Switzerland.
  • From the Ptschtal, Trentino-Alto Adige, Italy.
  • At the Trimouns talc deposit, six km northeast of Luzenac, Ariµege, France.
  • From Goepfersgruen, Bavaria, Germany.
  • At Snarum, Norway.
  • In the Onotosk deposit, Irkutsk, Siberia, Russia.
  • In the USA, near Fowler, St. Lawrence Co., New York; Delta, York Co., Pennsylvania; Smitheld, Providence Co., Rhode Island; Rochester, Windsor Co., Vermont; Holly Springs, Cherokee Co., Georgia; near San Andreas, Calaveras Co., California.