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Round white rock you can scratch outside off like chalk. Smaller one is starting to harden and form crystals.

+1 vote

asked Jul 16, 2017 by Vikings Valkyrie (130 points)

1 Answer

0 votes
I was thinking chalk. Limestone is chalk. If you mix some white vinegar with a little of that powder you should see a little bubbling. It should release carbon dioxide. Do it outside, just to be safe. Mix it in a glass jar. That will tell you whether it is chalk or not. You could do it with hydrochloric acid. Many times more powerful and not as safe. Safety glasses, rubber gloves, vented area, if possible outside...

Barite is another possibility, but barite is very heavy for its size. I will look up tests for barite, too, if you wish.
answered Aug 5, 2017 by Weasel (58,240 points)
Another possibility would be gypsum, especially if it crumbles easily. Can you stick a fingernail into it?