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I found this rock in Smithfield NC. It does scratch glass. A butter knife didn’t scratch it. When you hold it to a light it has an orange glow. It didn’t leave anything on porcelain.

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closed as off-topic by user12525, Peter Jansson, trond hansen, Erik, arkaia Sep 4 at 13:58

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  • "Questions about rock identification requests are off-topic. For more information, see the announcement on meta." – Community, Peter Jansson, trond hansen, Erik, arkaia
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Looks like Quartz (massive transparent/translucent crystal or rock without cleavages and hardness of 6) with iron oxyhydroxide coating, hence the red color. Could also be feldspar there, and then it would be an alkali granite. Most likely product of a late magmatism, as a vein or something similar. (if my identification is correct)

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  • $\begingroup$ Need more details outlining your interpretation. $\endgroup$ – Etienne Godin Jun 14 at 12:40
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    $\begingroup$ Done, it should be a bit clearer now. $\endgroup$ – Matheus Jun 14 at 12:45
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Agate, possibly Flint but the regular banding evident in the third image makes me think Agate is the more likely answer. Agate is a form of Silica, it's usually hard enough to scratch glass and it comes in an extremely wide variety of colours.

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This is a quartz vein that has strong microfracturing and moderate hematite alteration. The fractures are filled in with hematite-rich fluids, which accounts for the red color. This is a good example of fluids filling in microfractures, which is a very common process in rock mechanics. The fracture-filling process occurs at depth within the earth's crust during the rocks formation.

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