Abstract:
A new mineral named mangazcitc was found in the Mangazciskoyc silver ore deposit (300 km east of the Lena river, 65°43'40" latitude, 130°20' longitude), in Eastern Yakutia (Sakha Republic, Siberia, Russia). The mineral was discovered among fissured, intensively serialized and pyritized granodiorites near a quartz-arscno-pyrite vein. It is associated with gypsum and chlorite. The mineral forms radial-fibrous aggregates of thin-lamellar individuals. The size of the fibers docs not exceed 40 pm at length and 1 pm across. Color white, streak: white; luster vitreous; transparent in individual grains. Non-fluorescent; Mohs' hardness 1-2. Density (calc.) = = 2.15g/cm3 (with empirical formula). Biaxial (sign not determined), a =1.525(9), R not measured, y = 1.545(9). The mean results of wet-chemical analyses arc as following: A1203 36.28, S03 28.81, H2Of 34.35, total 99.44, H20" 9.27 (wt %). The amount of H20 was not included in the total, nor used in formula calculation. The empirical formula is Al199(S04)i.oi(OH)5.94 ■ 3.37H20; the simplified formula Al2(S04)(OH)4-3H20, which requires: A1203 37.47, SO, 29.42, H,0 33.11, total 100.00 wt %. Triclinic, unit-cell parameters refined from the powder data: a = 8.286(5), b = 9.385(5), с = 11.35(1) A, a = 96.1(1), (3 = 98.9(1), у = 96.6(1)°, Z = 4. Strongest X-ray lines d(I): 8.14(19), 7.59(49), 7.16(46), 4.258(100), 4.060(48), 3.912(43). Origin of the mineral is the su-pergene one connected with favorable aluminosilicate conditions and the presence of sulfate ions due to pyrite oxidation.