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Geology/Rock Id.


Diamond or topaz?
Diamond or topaz?  

Meteorite? Black, Heave, Magnetic, Looks melted on one side.
Meteorite? Black, Heav  
Could you please help me identify these rocks. I am a major rock hound and live in Northern Illinois, Slim pickings around here! All these rocks were found in the area.


Hi Brian,
The images are just too blurry and dim to make much out about them but I can take a shot at an ID.

The glassy looking one is more likely to be quartz than topaz or diamond because of the rarity of both. The best way to find out is to take it to the Geology department of a local university.  They are usually more than happy to help.  Another source can be a gemologist at a jewelry store.  They should be able to ID it for you.  Hardness tests will be the best way to find out. Both will scratch quartz.

As to the metallic specimen. It looks like you may have polished one side, or at least cut a slab from it. The most definitive test for a meteorite are the Widmanstatten Patterns (also called Thompson Structures). These are nickel-iron crystals that appear on a polished surface that has been treated with nitric acid. I don't recommend doing that yourself since nitric acid is very potent. Here the astronomy department of your university will be able to help.

But, as with the glassy mineral, this is very rare as well. It is more likely that this is metallic slag; a waste product from the steel smelting processes. Slag is very useful and so is found everywhere. It's more likely to be slag, but I would certainly check it out at the university to be certain.

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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