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concave side up
concave side up  

concave side down
concave side down  
Thanks for helping me/ This rock from north Cascades Mtn range Wa State [western] I found at bottom area of gradient as alluvial deposit [or start of alluvial fan] from mountain creek/ This rock looks "molten" and unlike most other rocks that are rounded as old river deposits/ It weighs 12lbs/ has no cleavage [ie shist/gneiss] but resembles "large, greenish oyster shell in contour/shape"the underside has goldish/iron/rusty-like specs [which is concave underside: From mainly Mesozoic/Crystalline/metamorphic period [CASCADE MTNS]/ The closest active volcano is Glacier Peak to south and Mt Baker to north/ Thank you for helping me!

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Hi Brad,
Interesting looking rock, and you've given much information, but the image is very blurry so I can't tell much from it.  However, I get the feel, from what I can make out, that it's probably a glauconite rich mica schist.  The rusty looking specs (biotite/muscovite# and greenish color #glauconite# allow me to lean toward that ID.  Also, as you mention, the Cascade Range is rich in metamorphic rocks.  It's not volcanic.  The "molten" appearance is due to a characteristic of most schists#  What happens is, the temp and pressures force the minerals in the rock into "layers" #well, not really "layers" we call them foliations, but "layers" make a better description) and orient them so they seem to flow#  The rock can look very much like it was molten#

Here's some examples of mica schists#  They aren't as good as I'd like, but I think they will show what I mean:

http://core#ecu#edu/geology/harper/Metamorphic/display_new#cfm?ID=7  

http://www.pi.ac.ae/PI_ACA/pge/facilities/img/rock_min_collection/9_m.jpg

http://www.quarry-machine.com/mica-beneficiation.php

Hope this helps.
Bob

Geology

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C. Robert Reszka, Jr.

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I can answer any general geology question (rocks, minerals, stratigraphy, geomorphology etc.). My expertise is in the geology of the Michigan Basin, PreCambrian, Paleozoic and Recent. I can answer questions concerning mining and petroleum exploration and production and the laws concerning those activities. I can also answer questions concerning stratigraphy of the Michigan Basin. I will also answer questions about mineral and rock collecting in the Basin. I won`t be able to answer many specific questions on hydrology, geophysics or geochemistry. I may be able to answer very general questions in those venues.

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I have been working for the State of Michigan for 36 years as a Geologist and a Resource Analyst. I have experience with Subsurface Geology and Petroleum Geology, mining in Michigan, and Sand Dune Mining and Protection issues.

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Michigan Basin Geological Society

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Decade of North American Geology.
Bedrock Geology of Michigan

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BS Wayne State University

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