“Asbestos” is not a single mineral. It is a commercial and regulatory term for a group of six naturally occurring silicate minerals that share a common trait: they crystallize into long, thin, durable fibers that can be separated and woven, spun, or mixed into products. All six are recognized human carcinogens, and all six cause mesothelioma, asbestos-related lung cancer, and asbestosis.

The six regulated asbestos minerals fall into two mineral families:

Serpentine asbestos (1 type)

  • Chrysotile — “white asbestos.” The only serpentine asbestos, and by far the most widely used — roughly 95% of all asbestos ever used in the United States. Its curly, flexible fibers went into insulation, cement, floor tile, roofing, gaskets, textiles, and brake linings.

Amphibole asbestos (5 types)

Amphibole fibers are straight, stiff, and needle-like. They are more biopersistent in the lungs than chrysotile and are more strongly associated with mesothelioma.

  • Amosite — “brown asbestos.” The second-most commercially used type, valued for thermal insulation, pipe insulation, and cement board.
  • Crocidolite — “blue asbestos.” The thinnest fibers and the type most strongly linked to mesothelioma. Used in high-temperature and high-tensile applications and asbestos-cement pipe.
  • Tremolite — not sold commercially, but a common contaminant of chrysotile, talc, and vermiculite. A major exposure source through talcum powder and Libby, Montana vermiculite.
  • Actinolite — rarely used commercially; occurs as a contaminant in vermiculite and other minerals.
  • Anthophyllite — the least common type; found chiefly as a contaminant of talc and some composite products.

Which types are the most dangerous?

All six cause disease, but the amphiboles — crocidolite, amosite, and tremolite in particular — are considered the most hazardous because their straight fibers lodge deep in lung tissue and resist the body’s clearance mechanisms for decades. Chrysotile, while less potent fiber-for-fiber, was used in such enormous quantities that it accounts for the majority of asbestos exposure and disease overall.

Where these fibers were used

The type of asbestos in a given product depended on the performance needed — chrysotile for flexibility and general use, amosite and crocidolite for heat and strength. Explore the product categories and manufacturers in the AsbestosIndex database to see the materials these fibers went into.

This page describes the established mineralogy and recognized health effects of the six asbestos minerals. It is educational information and does not constitute legal or medical advice.