Manganite from Black Jack mine, Nevada, USA

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Lustrous black crystals of manganite covering the top of matrix. In good condition. The Black Jack Mine in Pima County, Arizona, was a small underground manganese operation located within the Papago Indian Reservation. While exact permanent opening and closing dates are not recorded, primary historical production occurred during the mid-1950s (notably active in 1956), followed by additional intermittent development and working phases through 1958 and 1959, after which the property became idle. Geologically, the deposit is classified as a replacement-type ore body characterized by an east-striking bedding-plane fault featuring a quartzite footwall and a limestone hanging wall, with mineralization consisting primarily of psilomelane concentrated along the south wing of an apparent anticline.