The discovery of the Flambeau Deposit can be traced back to the early 1950's when Carl Dutton of the Wisconsin Geological and Natural History Survey showed a Kennecott geologist a copper-stained rock recovered from a 1915 hand-dug well at a schoolhouse south of the town of Ladysmith. Although Kennecott was primarily interested in the copper-nickel potential of the Duluth Complex and the Mellen Gabbro in north central Wisconsin, some airborne electromagnetic surveys were flown over potential base metal localities. One of these was flown over the schoolhouse but the results were not encouraging. Kennecott decided that glacial overburden was too thick and eventually closed their Wisconsin office in 1962 without making any discoveries. In 1965 Kennecott opened an office to pursue possible copper mineralization in the Kona Dolomite of Michigan's U.P. The geologist in charge visited Madison and reportedly was shown the same copper-stained rock still sitting on Carl Dutton's desk.
Several things had changed since the early 1950's. Most importantly, exploration and research in Canada had defined a new type of ore deposit - the volcanic hosted massive sulfide. Jack Phillips, the Kennecott geologist, was familiar with this research having worked on these deposits. He visited the schoolhouse site several weeks later and became convinced that Wisconsin has the host to one or more massive sulfide ore deposits. The schoolhouse locality was the pivotal occurrence which spawned Kennecott's exploration effort over the next few years.
The new airborne electromagnetic INPUT system provided greater resolution and depth of penetration and flying began in May of 1967. The anomaly that was to become the Flambeau deposit was detected on the first line flown west of Ladysmith. In November of 1968 the first hole drilled on the property intersected 48 feet of chalcocite mineralization averaging 9.25% Cu and 0.049 opt Au. Additional holes established Flambeau as the first massive sulfide in Wisconsin. The style of mineralization being characterized by massive Precambrian chalcocite enrichment was entirely unexpected.
The deposit was delineated by drilling between 1969 and 1971. An Environmental Impact Report was put together in 1974 and approved by the Wisconsin DNR in 1976. The mining permit application hearing was canceled after Rusk County turned down the zoning request. The project was reopened in 1986, additional drilling was completed and the mine plan was radically changed. Instead of proposing to mine the entire 6-7 million tons of ore, a new EIS submitted in 1990 identified 1.9 million tons of supergene enriched ore no more than 225 feet below the ground surface. This ore averaged 10.9% Cu and 0.088 opt Au and was direct shipping ore - no processing beyond minor crushing would occur on site. In addition the pit was to be backfilled and not flooded. Permits were issued in January 1991 and construction began in July 1991. The first ore was shipped in May 1993 24.5 years after discovery.
During 1996 the east end of the pit began to be refilled with low-sulfide waste rock mixed with lime to neutralize anticipated acidity. Active mining ceased in March 1997 although ore stockpiled on site continued to be shipped through July or August 1997. The pit has since been refilled and the land surface has been returned to a combination of wetland and low rolling topography.