I was visiting an elements exhibition in the Ulster Museum (Northern Ireland) and there were these native sulfur crystals on display.

Ulster Museum sulfur crystals

My question is how do sulfur crystals like these form in nature? Does the sulfur precipitate out of a solution? Are they the product of a chemical reaction? I am confused because of sulfur's negligible solubility in water and I couldn't imagine any other way such perfect crystals could form.

I am really interested in making such crystals myself but as I have said, I don't know by what process or under what conditions this crystallization of sulfur occurs.

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    $\begingroup$ Nature makes huge crystals out of many things; there is no guarantee that you can reproduce those even in a well-equipped lab. Negligible solubility over a million years may pretty well yield something worthwhile. Then again, maybe it was formed in an entirely different way. Slow cooling of molten sulfur, for example - why not? And by slow, I mean really, really slow. No, I mean even slower than that. $\endgroup$ – Ivan Neretin Mar 23 '17 at 16:02
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    $\begingroup$ Hint: by slow temperature lowering of molten sulphur, near volcanos, for example (en.wikipedia.org/wiki/Sulfur#Natural_occurrence). $\endgroup$ – Buttonwood Mar 23 '17 at 18:05
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    $\begingroup$ Crystals like the lower specimen, with large yellow crystals, couldn't come from cooling molten sulfur. Rather they would be made from an aqueous solution where there was a very low concentration of elemental sulfur depositing out. $\endgroup$ – MaxW Mar 23 '17 at 18:09
  • $\begingroup$ I used to dissolve sulfur in carbondisulfide and acetone, and some pretty cool little crystals would form if a tube of it dried out. By "pretty cool" I don't mean anything like what's in that photo though. $\endgroup$ – airhuff Mar 23 '17 at 20:17

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