Dwarven Mining Helmet, 1647 GUE    

The dwarves have always been the best, and only, miners in the land of Zork. Although they were seldom seen in the land of Quendor, the Third Age of Magic saw a tremendous rise in the dwarvish population in the Eastlands. Their obsessive mining projects added to the economic and technological rebirth of the through through their thorough and obsessive mining projects. The tunnels and tracks of their mine catacombed mountains across the Eastlands. From these mines, they extracted minerals needed for metals, as well as silver and gold. Every mine was overseen by a Head Dwarf Miner.

The first illuymnite mine was dug in the Dwarven Mountains northeast of Shanbar in the Valley of the Sparrows.
(see 'Dwarven Mountains' for more information)

SOURCE(S): Return to Zork (game, official backstory), A History of Quendor