It's likely a coal clinker. It's a waste by-product from burning coal. People find them all the time along railroad tracks and bring them to our Astronomy Club thinking they're meterorites.
Here's some free advice.. The Railroad owns EVERYTHING in its Right-of-Way. That usually includes 50-meters either side of the tracks. Next time you find something, keep the location to a County, or State.
If someone on here posted something like a moon rock, I would not be shocked in the least bit because I have seen many first in my life on here and I have been all over, but at least once a week I learn something here or see something new.