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Identity HelpMillard County Utah

10th Aug 2022 21:17 UTCJen Tibbetts

This rock was found in Millard County Ut, on the shoreline of the "D M A D Reservoir". It looks like black tourmaline to me, but I noticed that there are several other minerals that look similiar to the tourmaline in those counties, so I'm not sure which one it is.

My daughter's science teacher asked her to bring some rocks to school, so we need to know what they are before she brings them to share with her class. I have more that I'll post later. Please help if you know what they are.

Questions Answered
Can it scratch glass? : Yes
Can you scratch it with your fingernail? : No
Is it light/heavy for the size? : Heavy

10th Aug 2022 21:17 UTCJen Tibbetts

Same rock, different side

10th Aug 2022 23:24 UTCKyle Beucke 🌟

The black looks like it COULD be "hornblende" crystals and this could be an igneous rock, likely of intermediate composition (something like an andesite, perhaps?). But rock ID (especially of things like this) is difficult based on photos alone. Someone familiar with the geology (or Macrostrat?) might be able to nail it down.

Kyle

11th Aug 2022 00:15 UTCHarold Moritz 🌟 Expert

The geology around that reservoir is all alluvial and aeolian, so that rock was transported from somewhere else. It looks volcanic, with dark pyroxene phenocrysts? Not much else I can say.

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