Geology is a strange and fascinating field of study, particularly when it comes to asbestos. Asbestos is a group of minerals possessing useful yet deadly properties, composed of magnesium and silica. Crystals grow into hair-like formations, and were used in manufacture of thousands of construction products for over the past 100 years. If you live in Australia where it is now banned, you may encounter obsolete asbestos products in your daily life.
In raw state, asbestos filaments are chemically identical to solid ore. The difference is in the crystal structure. Alongside the half-micron wide crystal filaments is a dense rock formation made of the same silica and metal molecules. As a result of extreme conditions when the raw ore was formed, crystals grew in vacant pockets within the ore, forming friable, hair-like fibres.
Asbestos strands easily separate when handled, and break down into very light, microscopic fragments, capable of being suspended in air for long periods. When asbestos is airborne and inhaled, life threatening diseases develop as the fibres penetrate vulnerable tissues deeply, and can’t be removed. Decades may pass between exposure and diagnosis of asbestos diseases: asbestosis, lung cancer, pleural mesothelioma.
Serpentine and Amphibole Asbestos
There are six types of asbestos which are well known, three of which have been exploited commercially for the past 150 years. One type, chrysotile, is referred to as serpentine form, and occurs as long, spiral fibres. The other 5 types have a needle-like appearance, known as amphiblole form. Recently, many more specimens have been discovered with similar properties, occurring as contaminants in deposits of minerals like vermiculite and talc. Descriptions for types of asbestos follow.
Crysotile - Once thought to be the least dangerous due to its serpentine form, chrysotile occurs naturally as long, silky, white fibres. Ancient people used it in lamp wicks and clothing. Deposits are located and mined primarily in Canada and Russia. Chrysotile has been used in textiles, rope and insulation, and accounts for about 90 per cent of commercial asbestos use worldwide.
Amosite - This mineral gets its name from the area is was first mined: Asbestos Mines of South Africa. Brown in color, amosite is nearly as deadly as its amphibole relative crocidolite. Most often appearing in insulation of heated piping systems, amosite was widely used in shipbuilding. From 1940 to 1980, amosite made up 5 per cent of the asbestos trade. Countless miners in South Africa and shipbuilders worldwide lost their lives from exposure to amosite.
Crocidolite - Also known as blue asbestos, crocidolite has been phased out of commercial mining and manufacture. Crocidolite has the longest fibre of the amphibole forms of asbestos, possessing a straight structure. This is the mineral that was mined in South Africa as well as Baryulgil, and was most often added as reinforcement to cement products. At the height of the asbestos boom, crocidolite accounted for just over 2 per cent of asbestos used throughout the world.
Actinolite - Fibres of this shiny green mineral are long yet brittle, spiny and hard to process. For these reasons, actinolite was not used in commercial manufacture of asbestos products. It is commonly found in metamorphic deposits of lime and iron.
Anthophyllite - Occurring in an array of colours from gray to brown, this name is Latin for clove, the most common hue for anthophyllite. Although this fibre can be spun into threads, chrysotile asbestos is preferred for this purpose. Anthophyllite has good insulating properties but cannot compete with amosite, which is more plentiful and less expensive to mine.
Tremolite - Tremolite is resistant to chemicals and heat, but its inconsistent nature and inflexibility makes it hard to work with. Crystals grow in a variety of colours from blue to yellow-green to gray.
Several companies are responsible for the widespread contamination of the Australian environment with asbestos. Thousands of innocents have needlessly lost their lives through careless disregard for human safety and health. Asbestos products have only recently been banned in Australia. Be aware of the presence of asbestos materials in your home, work place and community, and take precautions to prevent exposure.