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Geology/Rock identification


Hello Robert,
I found a rock that i've never seen before and it really caught my attention. Would you please identify it for me.
Thank you in advance.

Hi Robert,
The picture is a bit too blurry to get the best ID but it looks like a Concretion.  This image looks a bit like your specimen;

What usually happens is that a fine grained mud or sand becomes partly lithified and then new material floods in with the waters that surround the stone and that new material (usually silt or limestone or dolomite) recovers the stone.

Hope this helps.


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C. Robert Reszka, Jr.


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.


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.

Michigan Basin Geological Society

Decade of North American Geology.
Bedrock Geology of Michigan

BS Wayne State University

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