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The rock is beige, porous and has cavities. It was found in a mountain stream in Southern Alberta, Canada.

rock sample

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closed as off-topic by Leukocyte, arkaia, trond hansen, Fred, Jan Doggen Aug 30 at 13:26

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

  • "Questions about rock identification requests are off-topic. For more information, see the announcement on meta." – Leukocyte, arkaia, trond hansen, Fred, Jan Doggen
If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ Does it look like pumice? en.wikipedia.org/wiki/Pumice $\endgroup$ – Archa Jul 5 '16 at 23:17
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    $\begingroup$ Hello, and welcome to Stack Exchange. A picture would be really helpful. $\endgroup$ – Daniel Griscom Jul 5 '16 at 23:47
  • $\begingroup$ Sorry had an issue with picture earlier. Here you go. $\endgroup$ – Yvon Jul 6 '16 at 0:25
  • $\begingroup$ The under side does look like pumice. $\endgroup$ – Yvon Jul 6 '16 at 0:26
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    $\begingroup$ Welcome to Earth Science Stack Exchange. Please see our guidelines on rock identification requests and add the necessary information to this post. (It's definitely not pumice.) $\endgroup$ – kwinkunks Jul 6 '16 at 13:36
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I would go with tufa - freshwatter CaCO3 deposit. Check if reacts to 10% HCl

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    $\begingroup$ This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, provide answers that don't require clarification from the asker. - From Review $\endgroup$ – arkaia Jul 6 '16 at 17:56
  • $\begingroup$ Just wondering, what's wrong with this answer? It seems fine to me. $\endgroup$ – Antonio Jul 6 '16 at 18:32
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    $\begingroup$ seems a reasonable answer to me $\endgroup$ – haresfur Jul 7 '16 at 1:59
  • $\begingroup$ @aretxabaleta I agree with Antonio perfectly fine answer. What good is this site without some discussion? Scientific Discovery is a process of asking questions, so lets help the asker and not denegrate the answer because it isn't complete and requires feedback. Also vinegar maybe easier to obtain than HCL for the test. $\endgroup$ – Michael Wallace Jul 12 '16 at 16:07
  • $\begingroup$ @MichaelWallace, as far as I understand the site, it is not supposed to be a discussion forum, but rather provide answers to specific questions. If the answer needed clarification, then it is not an answer but a comment. I understand that there is a limit on reputation to post comments, but the answer as posted it is just a comment. If the answer is expanded the way Gordon Stanger does in his answer, then it would be a much better answer and way more useful in this site. $\endgroup$ – arkaia Jul 12 '16 at 17:32
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I agree with Imorgh, that it is almost certainly a bit of freshwater limestone. It contains the botryoidal open-space depositional texture, and other irregular 'flowstone' textures that one associates with carbonate deposition around roots, leaf litter and other organic remains. Over time the organics oxidize and disappear, leaving just the porous carbonate coating seen in the photo. It is probably a recent rock (in geological terms), and relatively soft. In the longer time scale such rocks usually erode into carbonate sand, or are cemented up with more carbonate (or rarely silica) filling in the cavities.

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