CHAIN SILICATES PYROXINE....
By : SUBHASH MOHAPATRA[ Ph.D INORGANIC.]
Formed by sharing of 0 atoms on 2 corners of each
tetrahedron with octahedral giving the formula (si03)n 2n-
..A large number of minerals from chain but variety of
different structure are formed because the arrangement of Td in space may vary
and thus affect the repeat distance along the chain.
e.g spodurene LIAL[(sio3)2] ,enstalite mg2[(sio3)2] and
diopsite pamg[(sio3)2] wollastonic ca3[(sio3)3] has a repeat unit of 3
tetrahedron while others may have 4,5,6,7,9 & 12 Td..
Double chains may be formed when a simple chain are joined
together by sharing oxygen. These minerals are called amphiboles and are well
known.
These are several ways of forming double chains, giving (si2o5)n
2n- ,(si4o11)n 6n- , (si6o17)n 10n- and others..
Asbestos minerals are the best known amphiboles based on the
structural unti (si4o11)n 6n-.
In these the tetrahedral may share 2 or 3 corners.
e.g tremolite ca2mg5[(si4o11)2](oh)2
crocidolite na2fe3’’’fe2’’’[(si4o11)2](oh)2
They contain hydroxyl group..which are attached to metal
ions.
The si-o bonds are strong and directional . adjacent chains
are held together by the metal ions present.
Thus the pyroxene and amphiboles cleavage readily parallel
to the chains ,forming fibres... they are called fibrous minerals..
The cleavage angle for pyroxene is 89 degree and for
amphiboles is 56 degree.
This is used as a means of identifying the minerals.
Asbestos minerals come from 2 different groups of silicates.
1.
The amphiboles 2. The sheet silicates.
2.
The amphiboles includes crocidolite(formula
above by mohan) –blue asbestos and others derived from it by isomorhopus replacement e.g
amosite/brown..
WE FURTHER TELL YOU ABOUT SILICATES INDUSTRY WITH DIFFERENT FORM...
THANKS
FOR READING...BY MOHAN KUMAR AND HEMANT UNIYAL....
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