| Sillimanite in India |
lVI. L. MISRA, M.Sc.
Pages : 65-69
DOI : 10.1080/0371750X.1944.11012046 |
| Abstract |
| DESCRIPTION
Sillimanite is an aluminium silicate (Al11 0 8 SiO 1 ) and
occurs as lon;..: needle like crystals or fiberous aggregates in the
inner zones of hornfels in the contact metamorphism of argillaceous
rocks. ·when pure it is colourless but often its colour
is hair brown, greyish green, greyish brown, greyish white or
pale-olive green. Its hardness is 6-7 and sp. gr. 3. 23-3.34.
Its crystals are transparent to translucent and show vitreous
lustre. It is absolutely non-plastic. In thin sections it is
colourless and optically positive. Its basal sections are almost
square and show diagonal lines of 010 cleavage. |
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