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Geology/green/blue rock


HI,, I live in ontario canada, I hav found a rock, that is kind of aqua marine in colour,,, greeny/blue, I am attaching a photo, hopefully you might me able to tell me what kind of rock it is,, thank you in advance.

Hi Deb,
Very interesting specimen.  You have an example of glass slag. It's basically rough glass from a blast furnace.  This was probably from a glass making operation, although slack from an iron furnace can be very glassy.  
It can have value as an antique since much was produced in the 19th century from iron smelting factories and from glass making facilities.  It was used for commercial purposes and for lamps, and jewelry.  I don't know how old your sample is or if there were any iron factories near the area.  You might be able to find out more if you take it to a local university or rock club.

Here's a picture that looks much like yours but without much of the surface discoloration.

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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