HardAssetsInvestor

Written by Tom Vulcan  |

August 17, 2010

Talc: An Innocent White Powder

Details

In the latest installment of our Strategic Metals series, we look at talc, a soft white mineral with uses in paints, plastics, and of course, baby powder.

 

 

Anyone with children is familiar with talcum powder—that loose, white powder used to prevent diaper rash. But talc itself isn't just white. It can also be black, blue, brown, grey, pink, silver and violet. It all depends upon the talc's chemical composition, and what proportions of such elements as aluminum, iron, manganese and titanium may also be present.

While talc may not have as many recreational uses as other white powders, we are much more likely to come across it in our everyday lives and to benefit from its use. In fact, talc is found in everything from animal feed to tires, and has been for millennia. As long as 15,000 years ago, cave dwellers used talc in their paints. For at least 5,000 years, it has been used in cosmetics, especially as a skin lightener, and 1,000 years ago, the Chinese began using it in their glazed pottery.

 

What Is Talc?

Talc, with a chemical formula of Mg₃Si₄O₁₀(OH)₂, is a hydrous silicate mineral made up of magnesium (Mg), silica (SiO₂) and water.

 

A Talc Molecule

 

Source: Luzenac Group

 

Composed of microscopic platelets held together by very weak bonds, talc feels soft and greasy to the touch—one of the reasons it is used as a lubricant. And if diamond is at one end of the Mohs scale of hardness with a measure of 10, talc sits firmly at the other with a measure of 1.

Talc boasts a number of important chemical and physical properties, including:

• Chemical inertness
• Fragrance retention
• Grease and oil absorption
• High thermal conductivity
• Hydrophobicity (nothing to do with rabies!)
• Lamellarity, or "platyness"
• Low electrical conductivity
• Luster
• Magnesium content
• Organophilicity
• Purity
• Softness (nonabrasive and unctuous)
• Whiteness

 

Except for soapstone (also known as steatite or "massive talc"), talc is most often used in the form of a powder. Usually produced by opencast mining, the extracted talc is sorted and then milled to the required particle size and particle distribution. Typical particle size can range from 1-15 microns.

Grain shape and size, together with its purity and even color, will also have a bearing upon what the talc is used for. Often, talcs are also treated; for example, talcs used in pharmaceuticals and cosmetics are often decontaminated using heat, while those used in the rubber and papermaking industries are coated with various chemicals.