dice coal

from The Collaborative International Dictionary of English v.0.48

dice \dice\ (d[imac]s), n.; pl. of {Die}.
   Small cubes used in gaming or in determining by chance; also,
   the game played with dice. See {Die}, n.
   [1913 Webster]

   {dice coal}, a kind of coal easily splitting into cubical
      fragments. --Brande & C.
      [1913 Webster]