I would say it's got to be either Bituminous or SubBituminous.. you really can't tell from looking, you have to do an analysis on the coal. which most mines or breakers in the states would do. I don't know about the mines where you are.
The only way to tell between Anthracite and Bit coal is to put a piece on a hot bed of coals.. if it's Anthracite, it will just sit there, maybe pop or flake a piece off when it heats up or water turns to steam in a small spot.. Bit will fume, smoke, catch fire, burn with a yellow flame, smoke will often be yellow-gray.
The brown gunk is probably moisture, the coal may have a lot of water in it, and it is mixing with the fly ash when the coal is burned, making a muck /mud in the flue pipes..
Can you store a quantity near the stove, and see if it dries out [weigh it before/after] or just burn it after it has had a week or two to dry?