Geology/heed help identifying rock
My uncle had a rock that he'd found in western Michigan, on a shoreline of a lake close to lake Michigan. The rock is large, approximately a foot wide by a foot deep, and it seems to be heavy for it's size. The rock has a dark green top which appears to be melted, and it chips easily with a hammer and chisel. Through the rock are green veins. I chipped some of the top green part and looked at it under magnification. It appears there are very tiny green translucent pieces along with the very dark green matte material. The rock itself is too hard to break, even a tiny piece. I cannot scratch it either. While I can chip the green material, I cannot scratch it. I've had a couple of rock hobbyists look at it, and both had no idea what it was, and I was offered a somewhat substantial amount of money for it. I do know it is not Michigan greenstone. Also, the green top layer is about half an inch to a couple of inches thick.
If it were me I would take the money and run. My first guess is that this is a piece of industrial waste, probably from a steel mill. You don't say where in western MI it came from, but if it is from lower MI and from the shores of Lake MI, then I think it is quite possibly waste from a steel mill that got moved around. The glassy part of it is probably just that, glass. Sand was used in some part of an industrial process and became molten and cooled as this glass you see. The coloration is because of contaminants - iron ore, some other chemical in an allow, etc. The side of the rock, the white part, is also quite likely part of the same process. Not knowing what the process was I can't speculate much more.
Now, if the rock was found in the UP, it is possible that it is glacial drift and could be natural (although its more likely to be some relic of the old copper mines, etc that were up there).
If you can give me more location information as well as perhaps more detailed photos (higher resolution), maybe we can come up with more details.
Hope this helps.