| A Study of Crystalline Phases in Sillimanite Bearing Rocks
of Chippilangso by X-ray and Infrared Techniques |
G. C. BHATTACHARYYA AND R. K. BORUAH,M. N. AcHARYA And S. N. SHARMA
Pages : 82-85
DOI : 10.1080/0371750X.1990.10823000 |
| Abstract |
| Four samples of sillimanite rocks of Chippilangso, Karbi Anglong,
selected on the basis of their colours, were investigated by X-ray
powder diffraction and IR absorption spectra. A variety of sillimanite
was found in the pink (PV) as well as in the silky white (QS) coloured
rocks, while another variety of the same mineral was found in the
white coloured massive rock (MS). Besides these, oc-quartz and
kaolinite were found to be the other major constituents of the rocks.
Also, the rocks were found to contain muscovite, magnetite, and
hematite as minor constituents. The yellow coloured rocks (WV)
were found to consist of only oc-quartz. Unit cell dimensions and densities
of the sillimanite form, occurring in MS, are: a1 = 7.459 A,
b1 = 7.649 A, C1 = 5.739 A, OC1 = fJ1 = ?'1 = 90°, · Dm = 3.25
gm.cm-3, Dx = 3.27 gm.cm-3, and of the sillimanite, occurring in PV
and QS rocks, are: a2 = 7.445 A, b2 = 7.636 A, Cs = 5.762 A,
oc2 = {J2 = ?'2 = 90o, Dm = 3·26 gm.cm-3, Dx = 3.28 gm.cm-3•
Both the varieties of the sillimanite were orthorhombic, and their
space group, determined from the systematic absences of their X-ray
reflections, was P2221• |
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