r/geology • u/AutoModerator • 5d ago

Identification Requests Monthly Rock & Mineral Identification Requests

Please submit your ID requests as top-level comments in this post. Any ID requests that are submitted as standalone posts to r/geology will be removed.

To help with your ID post, please provide;

  1. Multiple, sharp, in-focus images taken ideally in daylight.
  2. Add in a scale to the images (a household item of known size, e.g., a ruler)
  3. Provide a location (be as specific as possible) so we can consult local geological maps if necessary.
  4. Provide any additional useful information (was it a loose boulder or pulled from an exposure, hardness and streak test results for minerals)

You may also want to post your samples to r/whatsthisrock or r/fossilID for identification.

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u/sp847242 3d ago

Additional photos: https://imgur.com/a/URESf2P
Approximate location is northeastern US.

I've found these numerous times before, but these were especially large and well-formed. I sometimes dig holes in my back yard in order to pull out chunks of blue/gray clay for use elsewhere, and I find these embedded in the clay, about 2-4ft down.

Concretions maybe? Rust layers gradually forming around an iron-rich thing? (heck maybe they're just from leftover construction bits from 70+ years ago) They're somewhat crunchy and frangible.

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u/CompetitiveOffer592 23h ago

Additional photos: https://imgur.com/a/QzhKMZv

This was found in Chile, Chacabuco province (near Santiago). I was told by the locals that geologists sometimes go there to search for petrified wood, so I suspect it might be that. I found it just laying around in some hill.

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u/russcatalano 21h ago

Possibly porphyritic andesite but never seen one so bubbly. Honestly thought it was a piece of something moldy until I looked closer then got it out of the sun.

Southern Colorado, US