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Post by Jugglerguy on Apr 2, 2012 22:07:20 GMT -5
These rocks are all over the beach at Black Rock on Presque Isle in Marquette, MI. They are various colors, but mostly green and red. The big one might be something different, but was on the same beach. Any idea what they are? flic.kr/p/bvg69AThanks, Rob
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Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Apr 6, 2012 0:21:04 GMT -5
It's rhyolite or basalt that was fractured by earthquakes, and the fractures filled with quartz.
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Post by Jugglerguy on Apr 6, 2012 7:51:56 GMT -5
Thanks Daniel. I was starting to think that no one knew what it was. Do you think it will tumble well?
Rob
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Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Apr 6, 2012 17:04:53 GMT -5
No, I doubt it will tumble. The rhyolite I've collected on the North Shore is seldom hard enough to tumble, basalt won't really tumble either. That could be calcite in the cracks too and not quartz. That would break apart even worse. If one of the pieces has a hard smooth surface you could give it a try -- throw it in with other rocks and see what happens. Shouldn't hurt anything.
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Post by Jugglerguy on Apr 6, 2012 20:12:35 GMT -5
It seems hard, but I haven't done and scratch tests. I think I'll do like you suggested and just toss one in with something else.
Thanks, Rob
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