Identity HelpUnknown black white mineral
Some material I found in Michigan. It was found in the Lower Peninsula near Bay City, but it was near train tracks, so may have been quarried and brought in from any where in the state. Rockport Quarry in Alpena and Bayport (in Bayport) are both big Limestone quarries that I'm sure has trucked material all over the state.
This material is hard and is not scratched by a steel knife and has no reaction to acid.
It does not appear to be translucent, but the pieces I checked may have also been too thick. Some pieces show some fracturing, kind of conchoidal, but a little different.
Most of the material is banded or spotted. My first instinct was Flint, as there is abundant Flint found just at the start of the Upper Peninsula.
The first image shows a piece with a great pattern, the second image a brown/white piece, and the third piece in the middle of a matrix (the top and bottom are both matrix, probably limestone)
Any ideas?
Seems to qualify as chert or flint (which are pretty much the same substance).
The first piece is rather pretty. I'd keep that in the collection, if I'd found it. I'd also go with chert/flint; the distinctions between the two, well, we could argue for a fortnight. I agree that the one in the first photo is interesting - a keeper. The other two....I don't know. As for location, as you say, could be from anywhere. If you catalog it, state where you found it, and add your thoughts that it may have come from xxx or yyy. Gives some ideas as to the actual source. Awesome. Thanks for the help. I kept thinking chert/flint, but thought it was weird it was all over the tracks.
I found last night on Mindat a quarry about 30 minutes away whose main commodity is chert, so I think that's a great option. Might go check it out and compare. 
One thing to note about railroad tracks is that you can find almost anything along them. I agree those are all keeper pieces of chert. One thing to note about railroad tracks is that it’s against federal law to be on the tracks at all, much less stealing rocks from their roadbed.
Just FYI Robert did say "near" train tracks, not on the roadbed, so let's not start implying he's a criminal. 
So true Doug.
A number of times I have gone back to the literature to sort out in my mind the difference between flint and chert. It appears that flint can be chert but if there is evidence of biogenic origin then chert cannot be flint. In other-words, chert is the "global" term when the genesis is uncertain. Then again some "experts" describe flint as nodular chert. Go figure, one of the more ubiquitous minerals is one of the most enigmatic.
