Any of six naturally occurring minerals characterized by being extremely fibrous (asbestiform), incombustible, and having high tensile strength. Historically they were utilized in commerce for fire protection; for fiber reinforcing material in tiles, plastics, and cements; for friction materials; and for thousands of other uses. Currently the vast majority of asbestos used worldwide is chrysotile type which is used for asbestos-cement production, while use continues to be strong only in friction products, coating and compounds, and roofing products.

Because of great concern over the health effects of asbestos, many countries have promulgated strict regulations or bans on its use. The six minerals designated as asbestos also occur in a nonfibrous form. In addition, there are many other minerals which occasionally occur naturally with a highly fibrous morphology similar to asbestos. These ambiguities generated a controversy over whether the mineralogical definition of asbestos fibers should be applied when doing health hazard evaluations for legal and regulatory purposes. The U.S. Occupational Safety and Health Administration (OSHA) has reviewed this matter and concluded that the medical and scientific information available does not support an expansion of the definition of asbestos to include minerals not mineralogically defined as asbestos in the regulations.