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Author Topic: what is this rock?  (Read 3773 times)

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!


 

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.
 

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.
 

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. ;-)
 

Offline macjonny

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

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.
 

The Naked Scientists Forum

Re: what is this rock?
« Reply #5 on: 10/02/2012 11:11:27 »

 

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