what is this rock?

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Offline Ladybugster

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what is this rock?
« on: 09/07/2011 02:17:55 »
I found these on the Lake Superior shoreline. Can anyone tell me what they are called? It's light black with green flecks, and I think they're cool!

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Offline Bass

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what is this rock?
« Reply #1 on: 09/07/2011 06:46:13 »
Looks like plagioclase phenocrysts in a fine-grained (or aphanitic) mafic groundmass- basalt or andesite.  Greenish color in the plagioclase may be due to alteration to chlorite or sericite- or may be from weathering.  There are plenty of mafic rocks in the Lake Superior region.
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

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Offline JimBob

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what is this rock?
« Reply #2 on: 04/08/2011 23:13:40 »
What he meant to say is this Looks like large crystals of a type of feldspar in a fine grained volcanic rock formed from the same material that forms the floors of the ocean. Since the rock came from the Lake Superior area it is VERY old.
The mind is like a parachute. It works best when open.  -- A. Einstein

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Offline Saille

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what is this rock?
« Reply #3 on: 09/10/2011 00:44:27 »
What he meant to say is this Looks like large crystals of a type of feldspar in a fine grained volcanic rock formed from the same material that forms the floors of the ocean. Since the rock came from the Lake Superior area it is VERY old.

I am glad there are translators on this forum. ;-)

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Offline macjonny

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Re: what is this rock?
« Reply #4 on: 10/02/2012 10:36:50 »
<link removed>

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Offline CliffordK

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Re: what is this rock?
« Reply #5 on: 10/02/2012 11:11:27 »
That last rock seems to be part of a geopuzzle from another site.

http://clasticdetritus.com/2010/02/04/geopuzzle-what-is-this-rock/
http://clasticdetritus.com/page/9/

And, of course, an unrelated link from the person posting it.