抄録
Kamiokite occurs as granular to thick tabular crystals with hexagonal outlines, up to 3 mm in diameter, in molybdenite-quartz veinlets in the Kamioka Ag–Pb–Zn mining area, Gifu Prefecture, central Japan. Chemical formula: (Fe2.01Mn0.03)2.04Mo2.98O8 on the basis of O = 8, or ideally Fe2Mo3O8. The mineral is hexagonal with space group P63mc, a=5.782(2), c=10.053(3) Å, Z = 2, cell volume = 291.09 Å3; calculated density = 6.02 gm/cm3. Strongest X-ray powder diffraction lines and their relative intensities (subject to preferred orientation): 5.03(100), 3.55(90), 2.509(75), 2.430(55), 2.006(40). Kamiokite is opaque, iron black in color, and metallic to submetallic in luster, with black streak. Cleavage [0001] perfect, fracture even. Vickers hardness (50 g load) is about 600 kg/mm2, Mohs hardness 4.5. Density measured 5.96 gm/cm3. In reflected light the mineral is gray with olive tint. Strong reflection dichroism, gray to olive gray. Anisotropism is strong, from light brownish gray to dark greenish gray. Reflectances (Rmax, Rmin) in air: 23.6, 16.0% (480 nm); 22.9, 15.3% (546 nm); 22.2, 14.7% (589 nm); 22.1, 14.3% (657 nm). The name is for the locality.
