Munakataite, A New Mineral From The Kato Mine, Fukuoka, Japan

摘要

Munakataite, Pb_2Cu_2(Se~(4+)O_3)(SO_4)(OH)_4, occurs as a thin coating on a fracture in a quartz vein containing Cu-Zn-Pb-Ag-Au ore minerals in the Kato mine, Munakata City, Fukuoka Prefecture, Japan. It is monoclinic with the space group P2_1/m and lattice parameters a = 9.766(8), b = 5.666(5), c = 9.291(10) A, β = 102.40(8)°, V = 502.1(8) A~3, and Z = 2. An electron microprobe analysis gave the empirical formula as Pb_(2.03)(Cu_(1.94)Ca_(0.01))_(∑1.95) (Se~(4+)O_3)_(1.00)(SO_4)_(1.02)(OH)_(3.92) on the basis of Pb + Cu + Ca + Se + S = 6 apfu and the calculated (OH) with a charge balance. Munakataite is a member of the linarite-chenite group, and it is the first selenite mineral in Japan, corresponding to a (SO_4)-dominant analogue of schmiederite. The mineral occurs as light-bluish aggregates composed of minute fibrous crystals up to 30 μm long. The calculated density is 5.526 g/cm~3, and Mohs hardness is less than 2.