Talc is type of clay mineral that contains hydrated magnesium silicate. Talc in the powder form is often combined today with corn starch and is used most often in baby powder. Talc also can be used as a thickening agent and as a lubricant for various consumer and industrial purposes. Talc is a common ingredient in paint and roofing products, ceramics and cosmetics. (geology.com)
Talc occurs in nature in foliated or fibrous masses and can exist rarely as crystals.
Talc is the softest mineral on earth with a 1 on the Mohs scale of mineral hardness. Any mineral that has a value of 2 or less on this scale can be scratched with your fingernail. When it is scraped on a plate of glass, it will produce a streak of white, but experts say this indicator is insignificant because the majority of silicate mineral will produce a similar white streak. Talc can be from translucent to opaque in its appearance, with a color ranging from white/gray to green. Talc cannot dissolve in water but can be slightly broken down in various mineral acids.
The mineral talc that is used to make talcum powder is formed by the metamorphism of several mangesian minerals: serpentine, pyroxene, ampibole and olivine when carbon dioxide and water is present. This is called talc carbonation or steatization. The process produces several types of rock close to each other called talc carbonates.
Talc is most formed by hydration and carbonation but also can form with a reaction between silica and dolomite. Also, talc can form from quartz and magnesian chloride.
Where Talc Occurs
Talc is a metamorphic mineral that is very common and occurs in metamorphic rock belts that feature ultramafic rocks, including soapstone. It also occurs in whiteschist and blueschist. A major example of whiteschists includes the belt in the western US called the Franciscan Metamorphic Belt. It also occurs in the western European Alps in Italy, as well as some of the Himalayas in India, Nepal, Bhutan and Pakistan.
Most of the major talc deposits in the US happen when heated water with dissolved magnesium and silica react with dolomitic marbles. Another type of talc formation happens when heat and active chemical fluids alter rocks, such as dunite and serpentine.
Most rocks with talc in the US exist in metamorphic rock in the eastern US in the Appalachian Mountains, and in rocks in Washington, Idaho, Montana, California, Nevada, and New Mexico.
Talc is used in many applications and is used to make talcum powder which is used in so many consumer cosmetics, including baby powder and makeup. Talc is used to make paper, plastic, coatings and paint, electric cable, food, drugs, and ceramics.
A high-talc rock that is gray or green in color is known as soapstone or steatite, and is often used to make sinks, stoves and electrical switchboards. Talc is often used to make table tops in laboratories and switchboards because it is resistant to electricity, heat, and acids.
When talc is very finely ground, it is used in talcum powder for cosmetics, as a lubricant in many industries and as a filler for making paper. It also is used for coating the insides of innertubes and rubber glubs to keep these delicate surfaces from sticking. With a high degree of refinement, talcum powder is used for baby powder. However, the American Academy of Pediatrics states that parents should not use it on babies because of possible respiratory problems, such as trouble breathing or even major lung damage if the baby inhales it.
Talc is further used as an additive in some foods and as a glidant in pharmaceutical products. In the medical field, talc is used to prevent recurrent pleural effusion, which can occur in mesothelioma. Talc can even be used to process white rice as a buffing agent.
Because of talc’s low shear strength, talc is known as one of the oldest solid lubricants in the world. Also, talc is used on a limited basis to reduce friction in some lubricating oils.
Talc is useful in the ceramics industry for both glazes and bodies. In art ware bodies produced with low fire, it gives whiteness and boosts thermal expansion so crazing does not occur. In stonewares, some talc is used to provide flux to the body and boost strength. It is used as a source of MgO in some high-temp glazes to provide control for the melting temperature. It can be used for a matting agent in some earthenware glazes.
More details about the most common uses of talc:
Cosmetics and Antiperspirants
Highly ground talc is used for many cosmetics. The very small talc platelets of the powder adhere to the skin but can be easily removed with water. The softness of talc allows it to be easily applied and taken off without abrasion to the skin.
Talc is effective in absorbing oils and perspiration made by human skin. Its good ability to absorb odor and moisture and lubricate the skin makes it a vital part of many antiperspirants.
The majority of pain is a suspension of mineral particles in liquid. The liquid part of the paint allows it to be applied, but after the liquid totally evaporates, the mineral particles stay on the wall. Talc is commonly used as a filler and extender in most paints. The talc particles have a platy shape and it improves how solids are suspended in the paint can. Powdered talc is extremely white in color and so is a great paint filler because it whitens and brightens whichever paint it is used in.
The majority of paper is made from wood pulp. The pulp is made from rags, wood and various organic materials. Highly ground mineral matters are added to the wood pulp to use as a filler. If the pulp is rolled into very thin sheets, the mineral matter fills up space between the fibers of pulp. This makes the paper smoother. Talc serves as an excellent mineral filler and boosts brightness, opacity and whiteness of paper. Talc can also improve the ability of paper to absorb many inks. The paper industry uses 16% of talc made in the US.
Talc. (n.d.). Retrieved from https://geology.com/minerals/talc.shtml
Talc Facts. (2018). Retrieved from https://www.nytimes.com/2018/12/14/business/talc-asbestos-powder-facts.html
Talc Ingredients. (n.d.). Retrieved from https://www.fda.gov/cosmetics/cosmetic-ingredients/talc