Asbestos
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Asbestos is a naturally occurring mineral which differs from other minerals in its crystal development. The crystal formation of asbestos is in the form of long thin fibers.
ASBESTOS
Source
Asbestos is a naturally occurring mineral which differs from
other minerals in its crystal development. The crystal formation of asbestos is
in the form of long thin fibers.
Geographical Source
Asbestos deposits can be found throughout the world and are
still mined in Australia, Canada, South Africa, and the former Soviet Union.
History
Over the years, asbestos had many uses. Its primary use is
as an insulator or fire retardant, but can also be used as a binder. Due to
this versatility, asbestos can be found in many types of building materials.
Even though the federal government placed a moratorium on the production of
most asbestos products in the early 1970s, installation of these products
continued through the late 1970s and even into the early 1980s.
Description
On the basis of the crystalline structure, asbestos are
divided into two mineral groups, as serpentine and amphibole. The amphiboles,
in their fibrous form are friable and so are the most carcinogenic, Serpentines
have a sheet or layered structure, whereas amphiboles have a chain-like structure.
Chrysotile (A, B) is the most common type of asbestos among serpentine group.
There are five types of asbestos in amphibole group and they are: Amosite,
Crocidolite, Anthophyllite, Tremolite, and Actinolite.
Chrysotile or white asbestos is obtained from Canadian
serpentine rocks. It is commonly used in industries. As it is less friable it
is less likely to be inhaled. One of the formula
given for Chrysotile is Na2Fe2+3Fe3+2Si8O22
(OH)2. Amosite is also known as brown asbestos or Grunerite
is an amphibole from Africa and the formula given for
Amosite is Fe7Si8O22(OH)2.
Crocidolite or blue asbestos is amphibole from Africa and
Australia. It is considered to be most dangerous type of asbestos and the
formula given for Crocidolite is Na2Fe2+3Fe3+2Si8O22(OH)2.
Anthophyllite, Tremolite, and Actinolite have their formula
(Mg, Fe)7Si8O22(OH)2, Ca 2Mg5Si8O22(OH)2,
Ca2(Mg, Fe)5Si8O22(OH)2,
respectively. They are less used industrially but are found in a variety of
construction mate-rials and insulations and also in some consumer products,
such as talcum powders.
Chemical Constituents
It is a double silicate of calcium-magnesium with little
amount of iron which gives colour to asbestos.
Uses
It is used as filtering medium for caustic alkalies, for bacterial
filters, heat resistant insulators, proof gloves, break lining, and fire-proof
clothing.
