Hey thanks for taking time to help me out! So I was able to chip a small piece off and put it under the brightest light I had and I see no hints of green. I took a look at it under a cheap handheld microscope and the only colors I can see beyond the brassy discoloration are the off white flecks and shiny black surface, almost metallic/iridescent looking. The brassy color goes from a rusty translucent film where it's thin to a pewter like luster where its thicker. But those are the only colors I see.
I talked to my dad and got some more specifics about where he found it. He said it was along a creek in the bottom of a ravine that used to be a riverbed for glacial waters. Lots of shale bedrock, sand, clay...sandstone further south. Also a large salt mine a few miles away on the lake.
If I wanted to get it tested, should I look for someone local or is it something I should take to the google and send it off somewhere?