The Dwarf King needs a weapon. Many cultures develop weapons from tools that are important to their everyday lives. What's more important to a Dwarf than the tool they use to gather shiney objects?
The King's pick is golden (in color, but not actually made of gold since gold is far too soft to do any serious mining with) with an aqua haft. He uses it to obliterate stone and enemies alike, stirring up some earth magics along the way.