From OSHKY Knowledge Library

Types of Asbestos Minerals

Source: US Asbestos Primer


More Common


"White Abestos"

3MgO-2SiO₂-2H₂0 White, Curly

(serpentine family)

Amosite (FeMg)SiO₃ Brown or Gray, Straight

(amphibole family)

Crocidolite Na₂O-Fe₂O₃-3FeO-8SiO₂-H₂O Blue, Straight

(amphibole family)

Less Common

  • Tremolite
  • Actinolite
  • Anthophyllite


  • Chrysotile is the only asbestos still mined and incorporated into products.
  • Amosite and Crocidolite were used pre-1970s-ish. Will be found in older buildings.

Health Effects

Ferruginous Bodies

  • Asbestos fibers are too small to be seen with a light microscope.
  • When asbestos fibers (and also glass and cotton fibers, talc, and graphite) become embedded in the lung, ferrous material coats the fibers creating ferruginous bodies, also called asbestos bodies.
  • Because more than just asbestos fibers can induce the formation of ferruginous bodies, the presence of ferruginous bodies does not necessarily indicate that they are "asbestos bodies." The person's work history must be considered to determine the type of ferruginous body.

Work Classification

The OSHA standard establishes a classification system for asbestos construction work that spells out mandatory, simple, technological work practices that employers must follow to reduce worker exposures. Under this system, the following four classes of construction work are matched with increasingly stringent control requirements:

  • Class I asbestos work is the most potentially hazardous class of asbestos jobs. This work involves the removal of asbestos-containing thermal system insulation and sprayed-on or troweled-on surfacing materials. Employers must presume that thermal system insulation and surfacing material found in pre-1981 construction is ACM. That presumption, however, is rebuttable. If you believe that the surfacing material or thermal system insulation is not ACM, the OSHA standard specifies the means that you must use to rebut that presumption. Thermal system insulation includes ACM applied to pipes, boilers, tanks, ducts, or other structural components to prevent heat loss or gain. Surfacing materials include decorative plaster on ceilings and walls; acoustical materials on decking, walls, and ceilings; and fireproofing on structural members.
  • Class II work includes the removal of other types of ACM that are not thermal system insulation such as resilient flooring and roofing materials. Examples of Class II work include removal of asbestos-containing floor or ceiling tiles, siding, roofing, or transite panels.
  • Class III asbestos work includes repair and maintenance operations where ACM or presumed ACM (PACM) are disturbed.
  • Class IV work includes custodial activities where employees clean up asbestos-containing waste and debris produced by construction, maintenance, or repair activities. This work involves cleaning dust-contaminated surfaces, vacuuming contaminated carpets, mopping floors, and cleaning up ACM or PACM from thermal system insulation or surfacing material.