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It is wrinkly from breaking apart at many seams (sorry, I do not know the technical terms), deep wine-brown with a white band, and hard enough that it is not creating a streak that I can tell. In fact, I couldn't break any off at all. I would say it is more lustrous than glossy.

EDIT: after looking at Jasper, i discovered Chert. folded ribbon chert, specifically, is apparently found in Golden Gate Park right here in my city. the picture looks exactly right.

enter image description here

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  • $\begingroup$ The other day I thought a stone looked like cookie dough, today it's a block of chocolate. Either I'm too hungry, or you guys need to stop finding your stones at the confectionary :-p $\endgroup$ – JeopardyTempest Apr 11 '18 at 17:15
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i found this to be the answer: it appears to be folded ribbon chert.

folded ribbon chert

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Looks very similar to the mineral jasper. Jasper is a microcrystalline form of quartz commonly known as chalcedony. The reddish color in your sample is likely due to the mineral hematite (iron oxide). Some consider jasper a rock since it often contains impurities. Jasper has a white streak which can make it hard to see on a white plate.

enter image description here

Source: http://www.minerals.net/mineral/jasper.aspx

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