I think it could be gypsum crystals but it is difficult to say without more data
Thank you a lot about the preliminary idea of the crystal, Can you please tell me that doing XRD of these sediments can help us identifying or confirming it. These sediments are from Andaman and Nicobar islands where it is every possibility of effect of tsunami in the past.
Dear Arindam, yes, using XRD you would be able to confirm it. Is this material in the top of the tsunamy bed? Are sandy o muddy facies?
these samples are from older sediments (Neogene) middle Miocene however there is effect of recent tsunami held in Dec, 2004.
Calcareous muddy facies
Dear Arindam, give some details on the optical properties of the grains.
What type of optical properties you mean ?can you please elaborate it then it will be helpful for me
Have you seen the grains under microscope? If so, then its properties under ppl and crossed-nicols may help in identification.
Grain in center seem to be a zircon. Pyramidal terminations are seen. Powder XRD can only help if your mineral is above 5% in whole sediment. Ideally, you can use EDS/EDAX attached to SEM, which can give you the grain chemical composition, and thus help identify. I can help analyse if they are few grains!
Other way is to make a canada balsam mount and use optical properties (as suggested by Dr. Basu) to identify them.
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