Asbestos is the common name given to a group of naturally occurring mineral silicates that can be separated into flexible fibres.  The name asbestos comes from the Greek word meaning unquenchable or indestructible. There are two main categories of asbestos namely serpentines and amphiboles.

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The serpentine family includes only chrysotile or "white" asbestos.  Chrysotile is the most commonly used form of asbestos. It has been or is currently mined commercially in Canada, the former U.S.S.R., Australia, the U.S.A., Finland, Greece, Bolivia, China, the Philippines and Southern Africa.  Only chrysotile was mined in North America with Canada at its peak producing about 20% of the world output. Chrysotile is found in over 95% of all asbestos-containing products.

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The amphibole family includes amosite, crocidolite, actinolite, anthophyllite and tremolite.  Only the first two of these have had any significant commercial use. Amosite (which is properly called cummingtonite-grunerite) is also called "brown" asbestos.  Crocidolite is also referred to as "blue" asbestos. These types have been or are currently mined mainly in Australia and Southern Africa. Production and use of crocidolite has recently been banned in most countries.

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Asbestos is found in large 'veins' in the host rock and as minerals they crystallise in narrow veins as parallel bundles of extremely minute fibres. Physical disturbance of these fibrous bundles generally breaks them down into even finer bundles of individual fibres.  A typical characteristic of asbestos is its very high length-to-width ratio of individual fibres. Asbestos is produced in a commercially useful form by successive stages of crushing and aspiration - similar to a vacuum cleaner lifting the fibres out of the rock. The fibres are then sealed in plastic bags and shipped to the consumer.

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Asbestos was a popular building material from the 1950s to 1990s. The main properties that make asbestos useful are its incombustibility, tensile strength and flexibility when separated as fibres, resistance to chemicals, and its effectiveness as a reinforcing or binding agent when combined with cement or plastic.  In addition, asbestos is a good heat and electrical insulator.

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Asbestos was often mixed with other materials making it hard to determine if the material in question contains asbestos.  If the building was built before 1990, it's likely that at least some parts of the building will contain asbestos. Common building materials that may contain asbestos include but not limited to:

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• Drywall taping compound (mud)

• Vinyl floor tiles

• Vinyl sheet flooring (linoleum)

• Ceiling texture

• Tile grout

• Mastics (glues)

• Roofing materials

• Vermiculite insulation

• Exterior stucco

• Interior wall texture finishes

• Cement shingles, boards, and drain piping

• Duct tape

• Widow putty

• Mechanical insulation (boilers, vessels, tanks, and pipes)

• Spray applied fireproofing

• Ceiling tiles

• Heat shielding

• Gaskets

• Fire stop

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