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Years ago, I bought from a flea market two strange looking stones, that the owner said he had found under the sand of a dune in the desert (I don’t remember which). Maybe it’s true, maybe not, but I liked their strange shape and they were cheap, so I bought two. Does anyome have any idea what they could be?enter image description here

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put on hold as off-topic by Universal_learner, Fred, arkaia, trond hansen, Jan Doggen Jul 12 at 9:37

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Please review our rock identification guidelines to provide the missing information so that your question is both answerable and useful to new users." – Universal_learner, Fred, arkaia, trond hansen, Jan Doggen
If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ does a magnet stick to them? $\endgroup$ – MaxW Jun 15 '18 at 0:33
  • $\begingroup$ @MaxW No, not at all $\endgroup$ – tommy1996q Jun 15 '18 at 9:14
  • $\begingroup$ The rocks appear to have a metallic lustre, is this so? Shape wise they look like well-corroded limestone like you would find in a cave or where the limestone is in contact with water frequently. The two characteristics do not work well towards an identification. Are the stones heavier than typical rocks of similar size? If they are heavier they could hematite. What desert do you think they were collected from. $\endgroup$ – Friddy Jul 11 at 15:46
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They look like ventifacts, wind polished stones from deserts or beaches. Identifying the mineralogy of such stones can be almost impossible without breaking them open due to the combined effects of very fine polishing and the build up of Desert Varnish on their surfaces. These specimens in particular appear to be very heavily varnished, as such I can't even guess at the underlying minerals or their arrangement.

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  • $\begingroup$ So the only way to know what they are would be breaking one of them? $\endgroup$ – tommy1996q Jun 18 '18 at 15:40
  • $\begingroup$ @tommy1996q You'd have to take a chip off each one to get a good look at what's under the varnish, it's almost certainly not worth it, they're beautiful specimens as they are. $\endgroup$ – Ash Jun 18 '18 at 15:44
  • $\begingroup$ Pretty sure the shape is not due to wind or at least it is not the primary factor with the shape, the location of the scallops are too random and there is no indication as to the general direction of the wind. $\endgroup$ – Friddy Jul 11 at 15:53
  • $\begingroup$ @Friddy There often isn't when dunes are involved as the stones don't remain in a single orientation the whole time they're being polished but get tumbled around as the sand under and around them moves. $\endgroup$ – Ash Jul 12 at 11:10
  • $\begingroup$ I could be wrong, I haven't seen too many ventifacts on dune type environments, I would expect that stones tumbling in sand would end up looking more rounded, which is why I believe the shape to be more from corrosion or solution effects rather than by wind weathering. $\endgroup$ – Friddy Jul 12 at 16:32

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