Columbite-(Fe)
Koss pit, Nine Mile Pluton, Wausau Intrusive Complex, Marathon County, Wisconsin, USA
Ferrocolumbite: A nice crystal blade with feldspar from dike #22, located in the Northwest corner of the Koss pit, and collected on May 30, 1999. So far ferrocolumbite has turned up in at least 8 of 31 described pegmatites, aplites and mineralized zones in the pit, though most are not as good as dike #22. Per information from Al Falster, these ...