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This is something I just picked up but wanted to know what it was. There are three types of substances combined to create this It's about 3inches each way.

Hi Mary,
Nice specimen.  It's really hard to ID a mineral from a pic but yours are pretty good.  I think the crystals on top are dolomite.  The color is right and the crystals are the right shape.  I noticed a metallic mineral that looks like pyrite.  The black coating is difficult to identify but I think, because of the other minerals present, it might be chalcopyrite.  However, there are many dark colored so I can't be certain.  More often a dark colored crust can form that is a mineral but is difficult to identify without a chemical analysis.  But I think I can see a sheen in the dark mineral that looks a bit like the multicolor you see in an oil slick.  That's indicative of chalcopyrite.
So, from what I can see, I think the pyrite is coated by chalcopyrite with a cluster of dolomite covering one side.
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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