慶北 奉化郡 將軍鑛山産 新種鑛物 將軍石에 對한 鑛物學的 硏究

Janggunite, a new mineral from the Janggun mine, Bonghwa, Korea

Wet chemical analysis (for MnO₂, MnO, and H₂O(+)) and electron microprobe analysis(for Fe₂O₃ and PbO) give MnO₂ 74.91, MnO 11.33, Fe₂O₃(total Fe) 4.19, PbO 0.03, H₂O(+) 9.46, sum 99.92%. Available oxygen determined by oxalate titration method is allotted to MnO₂ from total Mn, and the remaining Mn is calculated as MnO. Traces of Ba, Ca, Mg, K, Cu, Zn, and Al were found. Li and Na were not found. The existence of (OH) is verified from the infrared absorption spectra. The analysis corresponds to the formula Mn⁴⁺4.85M²⁺0.90Fe³⁺0.30)1.20O8.09(OH)5.91, on the basis of 0=14, or ideally Mn⁴⁺5-x(Mn²⁺, Fe³⁺)1+xO₈(OH)₆(x=0.2). X-ray single crystal study could not be made because of the distortion of single crystals. But the x-ray powder pattern is satisfactorily indexed by an orthorhombic cell with a 9.324, b 14.05, c 7.956Å, Z=4. The indexed powder diffraction lines are 9.34(s)(100), 7.09(s)(020), 4.62(m)(200, 121), 4.17(m)(130), 3.547(s)(112), 3.212(vw)(041), 3.101(s)(300), 2.597(w)(013), 2.469(m)(331), 2.214(vw)(420), 2.098(vw)(260), 2.014(vw)(402), 1.863(w)(500), 1.664(w)(314), 1.554(vw)(600), 1.525(m)(601), 1.405(m)(0.10.0). DTA curve shows the endothermic peaks at 250~370℃ and 955℃. The former is due to the dehydration and oxidation forming(Mn, Fe)₂O₃(cubic, a 9.417Å), and the latter is interpreted as the formation of a hausmannite-type oxide(tetragonal, a 5.76. c 9.51Å) from (Mn, Fe)₂O₃. Infrared absorption spectral curve shows Mn-O stretching vibrations at 515cm⁻¹ and 545cm⁻¹, O-H bending vibration at 1025cm⁻¹ and O-H stretching vibration at 3225cm⁻¹. Opaque. Reflectance 13-15%. Bireflectance distinct in air and strong in oil. Reflection pleochroism changes from whitish to light grey. Between crossed nicols, color changes from yellowish brown with bluish tint to grey in air and yellowish brown to grey through bluish brown in oil. No internal reflections. Etching reactions: HCl(conc.) and H₂SO₄+H₂O₂-grey tarnish; SnCl₂(sat.)-dark color; HNO₃(conc.)-grey color; H₂O₂-tarnish with effervescence. It is black in color. Luster dull. Cleavage one direction perfect. Streak brownish black to dark brown. H.(Mohs) 2-3, very fragile. Specific gravity 3.59(obs.), 3.57(calc.). It occurs as radiating groups of flakes, flower-like aggregates, colloform bands, dendritic or arborescent masses composed of fine grains in the cementation zone of the supergene manganese oxide deposits of the Janggun mine, Bonghwa-gun, southeastern Korea. Associated minerals are calcite, nsutite, todorokite, and some undetermined manganese dioxide minerals. The name is for the mine, the first locality. The mineral and name were approved before publication by the Commission on New Minerals and Mineral Names, I.M.A.