Look at what was mined in your area in days past. That will give you a good idea of what it may be. From the looks of it, it came from a highly fractured vein with hydrothermal inclusions. Those can be interesting to say the least. The pic at the bottom is what I am chasing right now. More than enough to go after. Just have to get an adit rehabbed first.
The reddish brown staining could be iron based or it something similar. I gave up trying to identify every specimen out there. I find something interesting, I crush it, pan it, and go from there. If I find enough to interest me, I'll send samples off. That is the only way to be sure.