Crocidolite asbestos fibers photographed by Daniel Friedman at McCrone Research (C) Daniel Friedman Types of Asbestos
Properties of Amphibole, Chrysotile, Crocidolite, Amosite, Anthophyllite & Tremolite Asbestos

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This article describes the principal types of asbestos and explains the differences among Amphibole, Chrysotile, Crocidolite, Amosite, Anthophyllite & Tremolite Asbestos.

This article series describes the physical properties of asbestos including its mechanical, chemical, electrical and related properties both in pure asbestos form and when asbestos is mixed with other materials like cement or rubber. As the author points out, while this is a lenghty article, there is far more detailed information about asbestos properties, chemistry, etc. Page top photo: crocidolite asbestos in the laboratory - ©D Friedman.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Types of Asbestos: properties of Amphibole, Chrysotile, Crocidolite, Amosite, Anthophyllite & Tremolite Asbestos

Asbestos ore showing parallel fiber structure - Rosato (C) InspectApediaProperties of Amphibole Group Asbestos

A review will also be made of the amphibole group of minerals which is generally identified by the formula 2CaO.5MgO.8SiO2H20. The actual composition of the amphibole fibers varies greatly, particularly in comparison to chrysotile.

[Click to enlarge any image]

The variation in composition results in a physical property change of the fibers. This variation requires more rigid controls for obtaining and identifying shipments of amphibole fibers.

Properties of Chrysotile Asbestsos

Chrysotile asbestos in rock form is usually found in soft shades of green; these shades range from a very pale green to a dark green. The Arizona asbestos is often pale yellow.

However, despite its original color, it in- variably becomes white or grayish white when it is opened or fiberized. Its commercial usefulness depends not so much on its chemical composition but on its physical properties.

For textile products, chrysotile asbestos is the most important type of asbestos used because it has the best combination of strength and flexibility. Its resistance to alkalies is very good. However, its resistance to acids is lower than that of other varieties. its specific heat is 0.266 Btu per lb per °F.

From the point of view of structure, chrysotile asbestos is considered a silicate with a sheet structure; this factor makes it the magnesium analog of the kaolin group. In most of its occurrences, chryso'tile which has serpentine or olivine - as its source rock, shows either none or very little ' lime. Its chemical composition is Mg6(0H)6(S4011)H20 or 3MgO-2SiO2-2H20. Chemical composition of fibers can vary from mine to mine, but this variation is not great when compared to the other asbestos fibers.

Although the fibrous structure of many chrysotile fibers is similar, there is often a difference in the operation of separating the individual fibers. Techniques and experience are required both at the mining site and in the manufacturing process in order to obtain good quality and fibrous structures.

Crocidolite Asbestos Properties

Crocidolite asbestos in the microscope (C) Daniel FriedmanCrocidolite, because of its distinctive color, is commonly known as blue asbestos. It is easily recognized by its blue color which appears both in its natural state and after fiberization.

When found in nature, the color varies from lavender blue to dark blue. Sometimes red and yellow streaks exist. When the fiber is opened, the dolor of the fiberized structure is lighter in shade than in its original form. The blue color is the result of the high soda content or the iron compounds associated with the rock formation.

Its general chemical formula is 3Na 2 O6FeO2Fe 2 O 3 16- Si0 2 11 2 0. Variation in the composition occurs where sodium may be replaced by potash, ferric or ferrous iron by magnesium or manganese and ferrous iron by aluminum.

The blue asbestos occurs only in very few localities and is mined only in large quantities in South Africa. Its predominate properties include high tensile strength, acid resistance, harshness and resistance to effects of outdoor exposure.

Amosite Asbestos Properties

Crocidolite as well as amosite occurs in metamorphosed siliceous-ferruginous sediments. The fibers are generally several inches long; however, the length is usually of no advantage inasmuch as its greatest use involves the manufacture of asbestos-cement products where fibers , of % in. or shorter are used. The more important features of amosite are its heat and acid resistant properties. In the rock form, it is gray to gray-green but when it is opened, it gives the appearance of a cloudy gray.

It may contain as much as 40 per cent iron oxide; sometimes, it is compared to anthophyllite. Unlike the true anthophyllites, amosite has long fibers and it is not as brittle.

Anthophyllite Asbestos Properties

Anthophyllite has a very limited use because of its weak fiber structure despite its resistance to high temperatures and chemicals.

Its low ignition loss is comparable to that of tremolite.

It is never known to occur with fibers that are sufficiently flexible to be spun.

Tremolite Asbestos Properties

Tremolite asbestos in the laboratory (C) Daniel Friedman Tremoite asbestos ceilint giles as fireproofing (C) Daniel Friedman

Tremolite asbestos (shown at above left under the microscope, and at above right as fire insulation on the basement ceiling of a commercial building in White Plains, NY) generally has weak and brittle fibers; its color ranges from gray to white.

Question: Is this U.K. Boiler Room Wall Material Asbestos?

Asbestos suspect boiler room wall material in a U.K. closet (C) DC Asbestos suspect boiler room wall material in a U.K. closet (C) DC

I would like to ask you whether this is asbestos. My building was built in 1985. - Anonymous by private email 2017/01/06

Reply: asbestos use bans vary by country

It would be odd for a home in the U.S. built in 1985 to use an asbestos-containing wallboard.

I can't see much and nobody can do an asbestos test by e-mail, but I agree that the wallboard in your photos looks odd:

Is this in an area where fire-rated board would have been installed?
How thick is the material?
Are there any stampings or markings?

If you're faced with creating a dusty mess or demolition I'd search for ASBESTOS TEST LABS and test a sample.

Reader follow-up: asbestos use on boiler cupboard walls in the U.K.

I live in England. This is wall cupboard where the boiler was fixed. The material is 1.5 cm thick. It is painted that's why I can't see any stamps or marks.

Asbestos suspect boiler room wall material in a U.K. closet (C) DC Asbestos suspect boiler room wall material in a U.K. closet (C) DC

Moderator reply: be careful with soft, friable asbestos-suspect materials

OK so as there is a boiler nearby it would be no surprise that the material is intended to be fire-resistant. There is a reasonable probability that this material in a U.K. building contains asbestos.

  1. The first, but incomplete, restrictions on use of asbestos in the U.K. were put in place in 1969.
  2. Earlier UK bans on new uses of amosite and crocidolite asbestos were put in place in the U.K. in 1985
  3. The U.K. didn't complete its ban on asbestos use until 1999.

So the material in your building could possibly include those forms of asbestos too.

Watch out: I would be particularly careful if as it appears, the material is soft. Cementious asbestos board products ("cement-asbestos-millboard") are quite hard, not friable, and of rather low risk unless sawn or chopped apart. But softer fire-resistant board can more easily be a source of dusty debris.

The term we use is "friable" which as a lay person I'd describe as follows: "If you can smash some of the material into small fragments or particles using just your thumb and fingers, then it's friable" - thus it can be more hazardous if disturbed.

Some thick soft friable asbestos-based material that I have inspected and tested in our lab contains high levels of tremolite asbestos that can be particularly hazardous. Photos are at ASBESTOS TYPES - I found thick tremolite panels in a U.S. (New York) building where it had been installed over a heating boiler as fireproofing.

Still the safest course is usually to leave the material alone unless it must be removed for other reasons. It can be coated, sealed, or covered-over with a material that remains acceptable and fire safe in the opinion of your building authorities or your local council.

If you can simply cover over the material the hazard will be less than if you disturb or try to remove it. It's not "radio-active" - it won't emit harmful particles into the indoor space if it is covered and protected from disturbance.

OR if you are faced with an unavoidable requirement to remove the material I would either treat it as hazardous asbestos-suspect material (PACM or "Presumed Asbestos Containing Material" ) or I'd have a lab sample tested. If you decide on testing do let me see the results.

UK Asbestos Use & Dates of Bans


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