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What type of rock is this?

 
 
Reply Tue 5 Jan, 2016 08:12 am
Found this small rock in southwestern Pennsylvania. Can anyone identify what it is?? It is brown, gray with small black specks and it has a lot of metallic pieces in it. http://s1379.photobucket.com/user/jimlisa10201/Mobile%20Uploads/story
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Type: Question • Score: 5 • Views: 1,412 • Replies: 4
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FBM
 
  1  
Reply Tue 5 Jan, 2016 08:21 am
Channelling farmerman...
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Lordyaswas
 
  1  
Reply Tue 5 Jan, 2016 11:35 am
My guess is granite.
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timur
 
  1  
Reply Tue 5 Jan, 2016 01:03 pm
More like this, in my view:

http://geology.com/rocks/pictures/types-of-peridotite.jpg
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farmerman
 
  2  
Reply Sun 10 Jan, 2016 05:49 am
@Jimlisa1020,
Thoe metallic piwces look like muscovite mica. AND, there is free quartz (thats important)
Igneous rocks are identified by a QAPF diagram as an id. Q-quartz/A-alkali feldspar/P-plagioclase feldspar/F-feldpathoid 'oids"" or dark minerals peridotite (USually dark minerals do NOT contain alkali feldspars or free quartz. Heres one I found over at Wiki, its pretty good (There are varieties of QAPFs) so put that term into a search engine when you have unknowns .ALSO grain size gives a name too (but its unimportant here). Your rock looks like a finer grained diorite or granodiorite
        https://upload.wikimedia.org/wikipedia/commons/thumb/7/77/Qapf_diagram_plutonic_05.svg/800px-Qapf_diagram_plutonic_05.svg.png
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