Fissure detecting at the Delaware Mine 

The Copperland team locates underground copper-bearing fissures at the old Delaware mine in Michigan's Keweenaw peninsula using methods both old & new: magnetic compass & Fisher Gemini-3 metal detector. - "Three fissures were developed to a considerable extent - the Stoutenberg, Delaware, and (Kelly) Hogan. The Stoutenberg was opened to the eighth level, the Delaware to the ninth level, and the Hogan to the fourth level... " - USGS Professional Paper 144 Butler & Burbank