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Gray rock
Gray rock  

gray rock
gray rock  
I have the rock or whatever it is and I would like to find out what it is. color is a dull silver, shiny in a few spots. It has tiny holes all over it. It is also very heavy for it's size.Magnets do not stick to it. Just very interested in knowing what this is.

Hi Paula,
There are many kinds of silver minerals and it is difficult to tell
one from another by just a picture.  But I think I can tell what you
have there.  It looks like a metallic slag.  That's the waste
product left over after the smelting process.  Slag can be glassy or
metallic, dull or shiny, silvery or gray to black.  It all depends
on what the original ore was and what kind of smelting process was

Your specimens look like a metallic silicate slag.  I have seen many
examples from all over the United States.  It is very useful and can
be found in road and train track ballast, brick and mortar, cement,
glass, or even jewelry.

I have been unable to find many images on the Net that display
specimens like yours to good advantage but if you navigate to these
sites you'll see an image that looks much like your samples:

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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