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What is Asbestos?

"Asbestos" is a general name given to a group of naturally occurring metamorphic minerals involving magnesium silicate that are fibrous. These minerals are characterized not only by their fibrous nature, but also by the many properties that has led to its widespread application. Such characteristics of asbestos are:

  • Consists of magnesium silicate
  • Fibrous crystals
  • Microscopic crystal fibers (3 to 20 micrometers)
  • High tensile strength
  • Flexibility
  • Resistance to chemical degradation (i.e. acid)
  • Resistance to fire
  • Low Electrical Conductivity
  • High Surface Area resulting from crystal fibers

There are six types of asbestos: Chrysotile, Crocidolite, Amosite, Anthophyllite, Tremolite, and Actinolite. Of these asbestos, only chrysotile, crocidolite, and amosite are used in industrial application. The other three asbestos types (anthophyllite, tremolite, and actinolite) are not used industrially. They are rare, usually being found as contaminants in other minerals.

These six asbestos types are further classified under two mineral groups - Serpentine and Amphibole. These groups are distinguished based on their crystalline characteristics.  Serpentine asbestos are those with curled fibers and Amphibole asbestos are those with needle-like fibers.

Chrysotile is the only type of asbestos that is in the Serpentine group.  Chrysotile is also the most used type of asbestos, as about 90-95% of all asbestos used in the United States being chrysotile.  Chrysotile, also known as white asbestos, is mainly obtained from Canada.  It is so widely used because it is less friable, meaning that it resists breakage more, and therefore will pose less of a hazard (won't be as easily inhaled) than the other types of asbestos.

Amosite and crocidolite are in the Amphibole group. Amosite, commonly known as brown asbestos, is the next most common asbestos used industrially. Amosite is usually obtained from South Africa. Crocidolite, commonly known as blue asbestos, is commonly thought of as the most dangerous type of asbestos. Therefore it has a highly specialized use in high-temperature applications. The amphiboles asbestos is more friable in their fibrous form, and thus more hazardous than Serpentine asbestos (chrysotile), although they also exist in safer non-fibrous forms.

"Asbestos" was so coined for commercial purposes, rather than for mineralogical reasons.  Because of their unique properties, particularly resistance to chemical and thermal degradation, asbestos became widely used during the Industrial Revolution (18th and 19th centuries) for insulation purposes for steam pipes, large kettles, boilers, kilns, ovens, and other high-temperature products.  Not limited to just thermal insulation, asbestos is also used as an acoustic insulator, fire-proofing material, and an ingredient in other building materials.

Products where asbestos are widely used in the present in the past include some of the following:

  • Cement Pipes and Sidings
  • Wallboards
  • Construction Mastics
  • Vinyl and Asphalt Floor Tiles
  • Adhesives
  • Fire blankets, curtains, and doors
  • Acoustical and Decorative Plaster
  • Insulation (Spray-Applied and Blown-In)
  • Electrical Wiring Insulation
  • Adhesives
  • Laboratory Tabletops
  • Elevator Equipment Panels
  • Caulking and Putties
  • Adhesives
  • Joint and Spackling Compounds
  • Roofing Shingles
  • Packing Materials
  • Chalkboards
  • Elevator Brake Shoes
  • HVAC Duct Insulation
  • Boiler Insulation
  • Ductwork Flexible Fabric Connections
  • Heating and Electrical Ducts
  • Roofing Felt
  • Thermal Paper Products
  • Electrical Cloth