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Warning: My calcite sample took two months to clean because I used the wrong acid.
I found a nice piece of calcite in a Missouri creek bed, but it was coated in iron oxide. I tried a weak vinegar soak for a few days, which did nothing, so I jumped to muriatic acid and it started to eat the crystal faces. I had to stop and slowly neutralize everything, then go back to a much longer citric acid bath. What's the safest way you've found to clean iron stains off calcite without damaging it?
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parkerb655mo ago
My own Arkansas calcite was ruined by a ten-minute phosphoric acid dip.
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ben4025mo ago
Oh man, @parkerb65, that's a tough lesson to learn the hard way! Phosphoric acid is no joke on calcite, it eats right through it. Ten minutes is basically a death sentence for a specimen like that. Always gotta test on a tiny chip first, no matter what the internet says. Really feels bad when a good piece gets turned to mush. Your poor Arkansas calcite didn't stand a chance!
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nora543mo ago
Depends on what you're trying to do... if you want a clean calcite crystal then yeah it's a disaster, but if you're trying to dissolve away the calcite to expose other minerals hiding inside, then ten minutes might be just right.
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