Table of Contents
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.
References
- Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
- Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
- Mindat.org. (2019). Talc: Mineral information, data and localities.. [online] Available at: https://www.mindat.org/min-727.html [Accessed 4 Mar. 2019].
