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Colorado Prospector - Gem and mineral prospecting and mining forums _ Gem and Mineral Specimen Finds or Processes _ Western Colorado Rock ID

Posted by: Flapjacks May 10 2018, 12:31 PM

I found this in Mesa County, associated with a mudstone formation. I don't know rocks too well, but it seems like a chert sandwich. Seems kind of familiar, like I may have seen something
like this outside of Colorado.

Anyone know for certain what this is and possibly some geological insight on such a formation?

Thanks for any help!

Posted by: Clay Diggins May 14 2018, 09:03 AM

Hard to tell from a picture but it looks like Calcite.

Have you done streak and hardness tests?

Posted by: Flapjacks May 14 2018, 12:12 PM

QUOTE (Clay Diggins @ May 14 2018, 10:03 AM)

Hard to tell from a picture but it looks like Calcite.

Have you done streak and hardness tests?

Probably should have done that first, huh? Scratched by glass easily and about a match for copper (stuff I have handy). Don't have a streak plate but lot of white coming off from scratching.

So yeah, calcite. Should have concluded that based on the fair amount of obvious calcite forming seams in the rock at the same site, but the look of this loose tan stuff threw me quite a bit.

Thanks!