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rock needs ID

Posted by craig johnson  
rock needs ID
March 07, 2013 07:41PM
sedimentary or metamorphic ?
open | download - 000_0997.JPG (414.2 KB)
avatar Re: rock needs ID
March 08, 2013 04:54PM
Craig, from what I can see in the photo, I would go with sedimentary. The particles appear to be quite mixed in size and it looks like the rock broke around particles and not through them (although a real close-up would help determine that). There is a slight indication of what could be foliation at the top, but I think it is an artifact.
Re: rock needs ID
March 09, 2013 01:54AM
Thanks for your reply Donald, The rock does react with hydrochloric acid, There looks to be some grain break opposite of the planar cleavage surfaces and are shiny spots through the break of the rock. Would that indicate a marble or would it be limestone ?
avatar Re: rock needs ID
March 10, 2013 04:34PM
If it fizzes everywhere with acid It would be limestone. If only in isolated spots, it could be another type stone containing small amounts of calcite. I would put my money on the limestone.
Re: rock needs ID
March 10, 2013 07:38PM
Hi, The rock might be a calcite cemented clastic sedimentary rock, such as sandstone. I'd try scratching a piece of glass with it. It it scratches glass, it's probably calcite cemented sandstone. It might also be a calcarenite--essentially a calcite sandstone. In either case, it looks sedimentary to me.

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