Talc is an alternative name for talcum, an industrial mineral of magnesium trisilicates with a chemical formula Mg3Si4O10(OH)2. It is pure in composition (oxygen, silicon, and magnesium). Sometimes, it is composed of other metals in small quantities, such as iron, manganese, aluminum, titanium, etc.
Talcum can be extracted from steatite or soapstone rocks with grey, white, and dark green colors depending on its composition. Steatites are talc-rich rocks while soapstones are an impure form of talc-containing rocks. Talcum is insoluble in water but is soluble in mineral acids, such as sulfuric acid, hydrochloric acid, nitric acid, etc.
Talcum is a soft mineral. The value of Mohs hardness is 1 for talc, similar to that of graphite. As the value of Mohs hardness increases, it means the mineral has greater hardness. For example, the Mohs hardness of a diamond is 10.
Talcum powder is a crushed form of talc. It is a white powder having a wide range of uses due to its highly absorbing properties. It is significantly used in cosmetics to keep the skin dry and for treating skin for bacterial infections. For healing purposes, it is used with a combination of other components as well.
Occurrence of Talc
In the 1880s, it was discovered on a local farm in Medoc. For the first time, it was mined and produced by Henderson Talc Mine in 1896. The second mine was Conley Mine which started work on the talc. Later, both merged into a single Canadian company known as Canadian Talc Limited.
Talc mineral mainly occurs in metamorphic rocks and metamorphic terranes, such as blueschist, whiteschist, etc. Whiteschist terranes included the area of the Franciscan metamorphic rocks of the western US and European Alps in Italy, Musgrave Block, Himalayas, etc.
In 2016, China was the only source of talc that produced about 2.2 million tonnes of talc. This is 30 percent of the global output of the talc. There are other countries involved in the production of talcum, such as America producing 9%, Brazil with 12%, India with 11%, France with 6%, Finland with 4%, and Russia, Austria, Canada, and Italy, with 2% each.
In the USA, talc deposits occur in several areas, including the Appalachians, Piedmont, Alabama, Nevada, Washington, Idaho, New Mexico, Montana, California, Texas, etc.
Talc can be obtained in large quantities from mines. For example, the Mount Seabrook mine is the second-largest mine of talcum in the world. A huge quantity of talc (about 400,000 tonnes) is produced by the mine located near Luzenac in southern France.
Talc is composed of two sheets, one is the trioctahedral sheet and the second one is the tetrahedral sheet. The structure of talc is like a sandwich in which a trioctahedral sheet is present in the center. Two tetrahedral sheets are arranged in such a way that one is above and the other is below the trioctahedral sheet.
This arrangement of sheets in the structure of talc mineral is known as tetrahedral-trioctahedral-tetrahedral layers (TOT). These layers of sheets are connected by weak Van der Waals forces. This enables the layers of sheets to slide over each other by applying external force. Due to this reason, talc minerals are very soft in nature.
These are two types of such sheets:
These sheets are composed of silicon ions that are surrounded by four oxygen ions. Silicon ions shared their three oxygens with the neighbor ions to produce a hexagonal sheet. One remaining oxygen ion makes a bond with the trioctahedral sheet for layered connections.
There are hydroxyl ions that are replaced by apical oxygens. In this way, they make bonds with the tetrahedral sheets. The structure of the trioctahedral sheets is similar to the structure of the brucite mineral.
The trioctahedral sheet is positively charged while the tetrahedral sheet is negatively charged. In this way, both the sheets cancel the effect of each other, and TOT layers become neutral. For example, Si4O104- is the composition of the tetrahedral sheet, while Mg3(OH)24+ is for the trioctahedral sheet.
Process of Formation of Talc
Talc is significantly formed by the metamorphism of magnesium-containing minerals. For example, serpentine, amphibole, olivine, etc. The reactions are carried out in the presence of water and carbon dioxide known as talc carbonation or steatization. Talc carbonates are produced as a result.
There are two main processes for the formation of talc. In the first process, magnesium and silica are added to a solution of heated water. In the solution, they react with dolomitic marble and replace it. For example, in Montana, there are large talc deposits produced by the replacement of marble. These deposits of metamorphic talc rocks are formed by metamorphosing of dolomite under high heat and pressure.
The second process is the alteration of heavy rocks that contain minerals known as mafic. These minerals are composed of magnesium and iron. When reactants react with the mineral they replace the mafic with talc. These deposits of talc are larger. For example, 100 meters in diameter and 300 meters in length, etc.
Talcum can be obtained from sedimentary rocks where they are converted into magnesium minerals. For example, kerolite, sepiolite, etc.
Talc can be produced as the result of the following reactions of minerals below:
- Formation of talc by hydration and carbonation.
- Talc formation by the reaction between dolomite and silica.
- Talcum can be produced by the reaction of chlorite with quartz.
Processing of talc from mines to mills
Open-cast or open-cut mining techniques are used for the production of talc. They are also known as mega-mining. In these mines, the ore containing talc is drilled and partially crushed into smaller pieces first. This crushed talc is shifted to the mills where it is further crushed and ground into small particles. For this purpose, several machines are used.
After the conversion to grounded form, it is ready for the removal of impurities. For removing the impurities, a flotation process is used and then the impurity-free talc is shifted for further procedure.
Effect of talc on the human body
Talc or talcum powder is non-toxic to human health as long as it is used externally. When inhaled, the following diseases may occur:
- Difficulty in breathing
- Chest tightness
- Acute respiratory stresses, etc
Does talc or talcum powder cause cancer in the human body?
It depends on the presence of asbestos in talc. Different pieces of evidence show asbestos talc is responsible for cancer in the human body. But asbestos-free talc has no such notable effect.
There are some cases of workers getting cancer in talc mines. It is primarily due to asbestos talc. Besides lung cancer, it has been found, that they have other diseases of the respiratory system. In the mines, many other minerals may be responsible for cancer. It may have been possible because of the radon deposits in mines.
It has been studied in several cases that talcum powder causes ovarian cancer. The transmission of talcum powder to the ovaries occurs when cosmetics products are applied to genital parts. The particles of talcum powder reach the ovaries through the cervix and fallopian tubes where they are thought to cause infections leading to cancer.
Based on this observation and facts, the international agency for research on cancer (IARC) has made the following points:
- Talc containing asbestos is a carcinogen.
- Talc lacking asbestos is not carcinogenic.
- The use of talc powder in the genital areas can lead to cancer.
15 Common uses of talc
Talcum is used for different purposes, some are mentioned below:
- Baby and adult usage powder
- Candy and chewing gums
- Foam packing
- Animal feeds
- Roofing products
- Wire insulations
- Ceramics (household uses)
- Plastics and rubber
- Cosmetic products
- Insecticide and fungicides carriers
- Paint products
- Chalk and sealants
- Sculpture stones
- Agricultural products
- Pharmaceutical products
Some of the most common uses are explained below:
In the USA, there is 24-26% usage of talcum in plastic products in a single year. It is mainly done to increase the strength of plastic products, such as polyethylene, nylon, polyester, polypropylene, etc. It also increases the heat-resistant properties of plastic products.
Talc is used in the paints to improve their quality. Talc powder is added to the cans of paints, being a very good filler. It also enhances the whiteness and brightness of the paints.
A large amount of talc is used in the cosmetic industry. It is used in powdered form to make it easy to apply to the skin and can be removed by washing. Talcum powder has absorbing properties. Therefore, when cosmetics powder applies to the skin, it absorbed the oils and sweat of the skin area.
It is used in the manufacturing of ceramic products, such as tiles, pottery, restroom fixtures, etc. It can be used as a filler to increase the strength and other characteristics of products.
The US used 15-17% of talc in ceramic products only in 2011. This will give you an idea of the ceramics application of talc.
Talc is used to increase the smoothness of the paper. Organic pulps are used in the manufacturing of paper and talcum powder is added to convert them into paper sheets. In this way, talcum powder fills the free spaces between molecules of pulp and gives smoothness to the papers.
In order to protect the roof from the ultraviolet rays and sticking, talc is used in several products of roofing materials. The USA consumed 5-6% of talc in the production of roofing products in the year 2011.
The impure form of talc can be extracted from soapstone. These stones have a larger amount of talc in them. They are used for sculpting purposes due to their softness properties. Soapstone is also used to obtain other minerals, such as chlorite, pyroxenes, micas, amphiboles, etc.
Talc is used as a glidant to increase the flowability of medicines products. It is also used as a pleurodesis agent to prevent the accumulation of excessive fluid in pleural spaces.
Talc is used as a food additive. It is also used as a buffing agent for the processing of white rice in the polishing stage.
Dermatological uses of Talcum powder
These are the following dermatological uses of talcum powder below:
- Talcum powder is used by mixing with aloe vera to soothe and refreshing of the skin.
- To prevent diaper rashes in children, it is usually used with zinc oxide.
- It also acts as a calming agent when applied to the body after being mixed with lavender plants.
- Talc powder also acts as an anti-bacterial agent for the skin.
- It can be used to absorb oils and moisture from the skin.
- It is used for skin areas prone to preventing heat and sweat.
- Talcum powder is used to reduce friction and chafing skin.
- It helps to stop fungal growth in the skin area.
Is talc a toxic ingredient?
Asbestos-free talc is non-toxic but can cause several conditions such as respiratory infection, coughing, fever, etc.
Why doesn’t talc absorb water?
It can absorb oils as well as water but only in small quantities.
What are the layers or sheets of talc?
There are two sheets of talc, a tetrahedral sheet, and a trioctahedral sheet. Both are bonded with each other in TOT form. The bonding forces are van der Waal’s forces.
What are asbestos talc and asbestos-free talc?
Asbestos talc is toxic and can cause ovarian and lung cancer. Asbestos-free talc is non-toxic.