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This rock was found in Indiana, USA.

It is large, egg-shaped and measures approximately 75 cm by 15 cm (2.5' by 0.5'). It is non magnetic.

What could it be that caused those lines?

enter image description here

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These are most likely quartz veins, hosted in a softer rock. It is all brown weathered, so it's hard to know for sure. My hints:

The lines you see are occasionally cross-cutting (i.e. top left of the image), which is a common feature of quartz veins in rocks. They protrude out of the rock, which tells me that it's very resistant material, relative to the host rock. This is an extremely common phenomenon. Sand is actually quartz left over after everything else has been weathered (dissolved, turned to dust or mud etc.).

I'm guessing that the softer host rock can be limestone or maybe shale?

A quick Google search shows up what these things look like before they become weathered.

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i do belive it is a clay/silt stone, and the lines and formations is most likely an ant colony or a termite colony that has been flooded whith muddy water.but some more information in the question is needed to be sure.i am not even sure it is a rock as it looks more like a lump of dry clay/mud.

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  • $\begingroup$ please dont downvote whitout putting in some sort of comment. $\endgroup$ – trond hansen Jun 4 '17 at 14:01
  • $\begingroup$ First of all, this is a rock.Dry clay or mud are indeed rocks. Termite or ant colonies are thicker than that. These are maybe 1 or 2 mm thick. The veins here are also crosscutting in what seems to be conjugate pairs with similar angles. This is consistent with tectonic fracturing, which would create a pathway for introduction of SiO2-bearing fluids, depositing quartz. If you're flooding the lines with muddy waters, that would be softer, not harder, than the host rock. Then the lines would be holes in the rock, not protrude outwards. Therefore, I think your answer is incorrect. $\endgroup$ – Gimelist Jun 5 '17 at 2:08
  • $\begingroup$ thank you for the comment,i dont agree whith your conclusion but thank you. $\endgroup$ – trond hansen Jun 5 '17 at 6:30

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