The Cobalt district is located within the Superior structural province of the Canadian Shield. Two distinct suites of minerals and age of mineralization occur throughout the region. The older are base metal sulfides associated with Archean volcanics and are classified as stratiform and syngenetic. The younger are the ore suites consisting of silver-cobalt-nickel-arsenic assemblages hosted within Archean volcanics and Huronian rocks and are fissure fillings and replacement veins. It was found through detailed research of ore samples that five typical assemblages of arsenides occur in specific parts of the ore veins at Cobalt. This specimen belongs to group 2, the Ni-Co-As assemblage, which typically contains a high Silver content and a predominance of nickel and cobalt arsenides. These assemblages were defined by William Petruk in the 1960's and published in "The Silver-Arsenide Deposits of the Cobalt-Gowganda Region, Ontario" (MAC). This specimen contains abundant Nickeline and Safflorite. It is a sawed and polished on one side which shows well the rosettes and veinlets of the ore minerals.
