I could tell you if I was holding it. Coal feels very lightweight in your hand, more so than you would think it would weigh for an object of its size. If it is lightweight like just mentioned, examine the colors on it. If you see any traces of a brownish color you have Lignite Coal, if its just black (excluding the goldish colored minerals that can be seen on this piece) you have Bituminous coal. It doesn't look glossy in this picture so I'm assuming it isn't Anthracite coal. If it doesn't feel really lightweight then it might be hornblende, but I'm not completely sure on that.
I have found similar pieces that were near the Missouri river that were shards of Indian pottery that had been thrown in a fire. some still showed the design work on the edges. Only a guess.....