As I said above large pieces like that are rare for anthracite even in this area to tell you the truth if I wanted to get anthracite that size I'd have to go pick it off the pile of raw mined coal before it went into breaker. Anthracite goes through additional processing to get different sizes. The largest you might find is stove and even that is not common. Stove is about the size of baseball or a little bigger.
The other thing is anthracite is more likely to shatter when you hit with a hammer, looks like yours is more into turning to dust.
The piece of ash you have there is more indicative of bone if it were anthracite which is rock with coal seams. Anthracite when fully burned is going to turn to an ash that is easily crushed. In a hand fired stove you can just about turn it to powder.