Amosite is also known as brown asbestos and sometimes "gray" asbestos and is, like crocidolite, a member of the Amphibole group. Its color comes from the natural presence of iron and magnesium found in this form of asbestos. Its harsh, spiky fibres have good tensile strength and resistance to heat. In buildings, amosite was used for anti-condensation and acoustic purposes; on structural steel it was used for fire protection. Between the 1920s and the late 1960s amosite was used in preformed thermal insulation, pipes, slabs and moulded pipe fitting covers. In the United Kingdom amosite was also used widely in the manufacture of insulation boards. The import of amosite was banned in the UK as of 1 January 1986 and in the United States in 1970. Amosite is a commonly commercially-used synonym of grunerite. It may also be calledferro-anthophyllite.
This form of asbestos was first found in South Africa and was mined extensively there. Amosite is considered to be one of the more hazardous forms of the material. Large numbers of South Africans who worked in the many asbestos mines there have come down with various forms of asbestos-related disease. Countless numbers have died.
Brown asbestos is now banned in most countries and has been for a number of years, but it can still be found in older products and structures, therefore still posing potential dangers. Because this form of asbestos is highly friable (breakable into small pieces that can be inhaled) it is especially dangerous.