The softest mineral on Earth ends up in plastics, paper, rice and pottery
Talc sets the bottom of the Mohs hardness scale at 1, soft enough to scratch with a fingernail. That softness comes from sheets of atoms held together by feeble forces that slide past each other. The same property made it one of the oldest known solid lubricants, and today plastics consume more talc than cosmetics do.
Chemically, talc is a hydrated magnesium silicate, and its name comes from the Persian tālk, a word once applied loosely to mica and selenite as well. It looks whitish grey to green with a pearly sheen and splits perfectly along flat planes. Each layer is a sandwich: two sheets of silica tetrahedra bonded tightly to a central magnesium sheet, forming an electrically neutral unit. Neighbouring sandwiches cling only through weak van der Waals forces, which is why they peel apart so readily and why talc feels slippery.
Most talc forms when magnesium-rich minerals such as serpentine or olivine are altered by water and carbon dioxide deep in the crust, a process called steatization. It can also grow where silica-rich fluids invade dolomite, or under the high pressures of blueschist metamorphism. Soapstone, a rock made mostly of talc, turns up in belts of ultramafic rock, from the Franciscan belt of the western United States to the Alps and the Himalayas, and talc-carbonate rocks are common in the ancient komatiite belts of Western Australia.
China dominates production, yielding about 2.2 million tonnes in 2016, some 30 percent of the world total, with Brazil, India and the United States next. The biggest supplier's flagship pit, Trimouns, close to Luzenac in the south of France, yields some 400,000 tonnes annually. In the United States in 2024, plastics took 32 percent of talc sales, where it stiffens polypropylene and improves heat resistance. It also fills paper, coats rubber gloves during manufacture to stop sticking, polishes white rice, and adds whiteness and strength to ceramics. Soapstone's resistance to heat and acid suits it to laboratory benchtops.
Health questions shadow its best-known use. The American Academy of Pediatrics advises against baby powder because fine particles can be inhaled and harm the lungs. The IARC rates talc contaminated with asbestos as carcinogenic to humans, and the American Cancer Society, like Cancer Research UK, describes the research on cancer links as mixed. Meanwhile, patents are pending on magnesium silicate cement that needs about 650 °C rather than the 1,500 °C used for Portland cement and absorbs carbon dioxide as it sets.
Source: Talc
