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Can you identify the minerals on this pegmatite?

+1 vote

asked Mar 4, 2018 by Rilkad (130 points)
edited Mar 12, 2018 by Rilkad

3 Answers

0 votes
yes of course
answered Mar 5, 2018 by manuelaaumick (430 points)
Can you help me? My grandfather gave it to me. But only said it was volcanic. I love it and would like to know more in detail. Apart from the quartz crystals of course. I would like to know the shiny minerals name, the dark greenish ones and the mudsrone in the middle.
The rock weighs 5.6 kg and is 25 cm long aprox.
 Thanks in advance.
0 votes
Seems most likely to be limestone and a bit of calcite or dolomite. Can't be sure but a drop of vinegar would give more clarity. Put a drop of vinegar somewhere inconspicuos, it will bubble if it is any of those three compounds. You can wipe it away as soon as the reaction starts. That is an acid test for confirmation.
answered Mar 11, 2018 by Weasel (58,940 points)
0 votes
The large beige "Clayey" type of mineral looks like it may be some sort of carbonate such as aragonite, or perhaps a pseuodmorph. It may also be a feldspar. As per Weasel's advice, an acid test would be helpful to determine it as a carbonate. As for the smaller black substance, can you please provide a better close-up?
answered Apr 30, 2018 by hershel (52,800 points)