Hard iron ore at the Cliffs Shaft Mines, Ishpeming, Michigan

At the Cliffs Shaft Mines, for many years the premiere hard iron ore mine of Michigan, bodies of ore typically are localized in the upper part of the Negaunee iron-formation, close beneath Goodrich Quartzite in the axial part of the Marquette synclinorium. Individual ore bodies may be as much as 100 feet thick and extend laterally for many hundreds of feet. The cluster of ore bodies making up the Cliffs Shaft deposit has an overall length of about 4,500 feet from east to west parallel to the axis of the syncliorium and a width of 1,500 feet from north to south. The deposit extends beneath much of the City of Ishpeming, from a short distance west of the city limits to almost the east edge of the city.