by Louise Schoneveld

Anthophyllite asbestos SEM
Anthophyllite asbestos in SEM image (scale 50microns)

Asbestos has become a scary word, but do you know what it is? It is actually a set of six naturally occurring silicate minerals that have an asbestiform crystal habit. This habit describes crystals that have a roughly 1:20 aspect ratio:

asbestos aspect ratio

The six minerals that have this asbestiform habit are:

  1. Chrysotile – Mg3(Si2O5)(OH)4 (WHITE ASBESTOS)
  2. Tremolite – ☐{Ca2}{Mg5}(Si8O22)(OH)2
  3. Anthophyllite – ☐{Mg2}{Mg5}(Si8O22)(OH)
  4. Amosite (grunerite) – ☐{Fe22+}{Fe52+}(Si8O22)(OH)2 (BROWN ASBESTOS)
  5. Crocidolite (riebeckite) – ◻[Na2][Z32+Fe23+]Si8O22(OH,F,Cl)2 (BLUE ASBESTOS)
  6. Actinolite – ☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2

Chrysotile belongs to the serpertine mineral group and the remainder are from the amphibole mineral group.

Asbestos Mining

Asbestos was mined just like any other commodity. In Australia, a large blue asbestos (crocidolite) mine was opened in 1938 in Wittenoom in WA. The mine was shut down by 1966 but the damage of mining the crocidolite was already made with dangerous amounts of fibres on the roads which can be kicked up by vehicles. Wittenoom has now been removed from road signs and all power and services have been shut down.

The 1990 Midnight Oil song, “Blue Sky Mine” was based on this town and its mining history.

Click the title of the song if you feel like watching former politician Peter Garrett’s unique dancing style. Warning: intense harmonica solo contained within.

Warning in Wittenoom
Warning in Wittenoom

why did we use it?

Asbestos has many desirable properties in buildings; including sound absorption, fire resistance and insulation. In Australia, asbestos was used in construction between 1946 and 1980. The use of asbestos was banned entirely in 2003.

There are two main types of asbestos used in construstion: (1) Bonded Asbestos: this is where the asbestos is held in another type of material (eg cement) and (2) Friable Asbestos: this is asbestos that is crumbly, dusty, powdery (DANGEROUS)

One example of friable asbestos is the “Mr Fluffy” insulation used between 1968-1979 in Canberra homes. Mr Fluffy is a finely crushed asbestos that was blown into the roof spaces of canberra homes. It is so fine that 2 million fibres can fit onto a 50 cent piece.

Why is it so bad?

As asbestos is a stable mineral it is theorised that the toxicity of asbestos is not chemical but physical in nature. Some fibres are so small that they destructively tangle with chromosomes which can cause cancer.

As blue asbestos (Crocidolite) has much smaller fibres it is considered more dangerous than white asbestos.

What now?

“In general, the presence of asbestos in residential and non-residential buildings does not pose a risk to health if it is in a bonded form and in good condition” – ACT Government, Asbestos Awareness

While exposure to asbestos is considered dangerous, the most important thing to note is that most cases of asbestos related illnesses and deaths are from people who work directly with asbestos. Also, the latency period (period between exposure and symptoms) can be as long as 25 years.

More Info

If you are worried about asbestos in your home:

http://www.asbestos.act.gov.au/

The website below includes a list of Mr. Fluffy houses in canberra. http://www.asbestostaskforce.act.gov.au/