So earlier today I had a dme brick that I laboriously broke up. A solid brick, not powdery in the middle. Hammer blows were not very effective so I used a combination of a chisel and drill with a screw tip.
I just discovered that this work is not necessary if u have some time. I left some big chunks in warm, ~130, water and it's melting. It's not fast, I think its taking 2 hrs or so for the 2 half lb blocks but it's going.
I figure I'd post it I case anyone else had hard bricks in their inventory. Happy brewing..