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Thread: What is this Rock?

  1. #1 What is this Rock? 
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    Really need help identifying this rock (not much of a rock expert )!
    A Little more info: Found lying amongst quite a bit of basalt and some common metamorphic rocks (gneiss etc...)
    Please help!
    ++2011-11-28_21-46-50_486.jpg


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  3. #2  
    Time Lord Paleoichneum's Avatar
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    not enough detail to give it a name beyond possible extrusive igneous rock


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  4. #3  
    Universal Mind John Galt's Avatar
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    Some thoughts:

    I'm not sure why Paleoichenum is suggesting an extrusive igneous rock. The crystal size is quite large, so cooling was reasonably slow.
    The texture appears more like a metamorphic one than an igneous one. There is definite orientation of mineral (though that is not uncommon in lava flows).
    The light mineral is probably a feldspar. There is a greenish tinge also which suggests an olivine or pyroxene.
    If this is igneous the large crystals are most certainly not in equilibrium with the melt. They are almost certainly ferro-magnesians silicates of some sort.
    I don't see any quartz.
    Do you have any other views of it? Especially one where the large crystals are not in shadow?
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  5. #4  
    Time Lord Paleoichneum's Avatar
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    I siad external extrusive due to the context where it was found and the large structures on the right face appearing to either be chipped surfaces or lichen/staining. The left face and top face both show a very fine mix of minerals with little in the way of distinct crystals.
    If more of us valued food and cheer and song above hoarded gold, it would be a merrier world. -Thorin Oakenshield

    The needs of the many outweigh the need of the few - Spock of Vulcan & Sentinel Prime of Cybertron ---proof that "the needs" are in the eye of the beholder.
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