“The Central Mine, like the Cliff and Copper Falls, was a fissure mine. Unlike a typical copper lode that could run for miles and miles, a fissure deposit was very localized. These fissure deposits also didn’t behave typically, running perpendicular to the ridges of the Keweenaw instead of along them, and dropping straight down instead of along an angled strike. The fissure deposit at Central was massive, dropping some 30 levels (and over 3000 feet) straight down into the earth.”