Since it was warm outside, I figured I'd poke around my firebox and knock down and accumulated ash in the corners, and pick out any clinkers.
I found quite a few nasty sized clinkers in there. I have recently burned UAE, somerset low vol bit, and barton md low vol bit. I'd be inclined to say these came from the UAE coal due to the color. The bit ash is gray.
Nearly had an outfite after digging around in the coal bed, but a few lumps of Valier's finest took care of that!