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Rao, N. K.
- Deformation Twinning in Stibnite from Punjab, India
Authors
1 Metallurgy Division, Atomic Energy Establishment, Trombay, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 7 (1966), Pagination: 28-32Abstract
Prismatic sections of stibnite obtained from-Punjab, India, show various types of twinning, whose nature indicates deformation origin of the twinning . The twinning is simple or repeated or polysynthetic; in the latter case the twin lamellae may be parallel, wedge-, lens- or spindle-shaped, twisted and sinuous.
The disposition of the twinning lamellae and their relation to the (010) cleavage indicate that twin gliding has taken place in the plane (001) along [010]. This is probably due to the least coherence along [010]. The various patterns of twin lamellae are due to (a) trans lation gliding (010) [001] (b) bending about [100] and © twisting about [001] subsequent to the twinning. The simple types of twins are either due to accumulation of localised stresses during alteration or due to grinding and polishing, and the complex ones are due to shearing movements during or after deposition of stibnite.- Alteration of Beach Sand Ilmenite from Manavalakurichi, Tamil Nadu, India
Authors
1 Ore Dressing Section, Bhabha Atomic Research Centre, Begumpet, Hyderabad - 500 016, IN
2 Nuclear Physics Division, B. A. R. C., Bombay - 400085, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 23, No 4 (1982), Pagination: 168-174Abstract
The study shows that the alteration of ilmenite has taken place according to the two stage model proposed by Grey and Reid (1975). Identification of the intermediate altered compound, pseudorutile, was found difficult in earlier studies by optical and X-ray diffraction methods, because of the occurrence of this phase in altered ilmenite in very fine grain size (30 Å), its poor crystallinity and coincidence of many of the diffraction lines with those of other phases. The present study has shown that the Mossbauer technique is more suitable in the identification and estimation of this phase.
The relative amount of pseudorutile increases progressively in the magnetic fractions in the following order: 0.30 - 0.35 amps (5%), 0.25 - 0.30 amps (40%), 0-0.25 amps (75%) and 0.35 - 0.50amps (95%), indicating that the magnetic susceptibility of the grains is increasing initially with progressive pseudorutile formation, and decreasing in the later stages of alteration. Reflectivity and hardness are also increasing up to the stage of pseudorutile formation and decreasing in the later stages.