抄録
The electron microprobe analysis of tinticite from the Suwa mine, Nagano Prefecture gave Fe2O3 50.49, P2O5 29.57, V2O5 0.60, SO3 0.38, yielding the empirical formula Fe3+5.95 (P3.92V0.06S0.04)Σ4.02O19 on the basis of O=19. The original formula Fe3+3(PO4)2 (OH)3 · 3.5H2O requires H2O 19.16, thus the sum being 100.20%. The X-ray powder pattern is indexed on an orthorhombic cell with a=20.85Å, b=13.51Å, c=15.82Å, Z=16. The calculated density is 2.76 g/cm3, close to the original value, 2.8 g/cm3. The discrepancy to the monoclinic cell derived by Melgarejo et al. (1988) is accounted for. It occurs on thin coating or massive filling on void walls in rough goethite-jarosite ores that precipitated from a hydrothermal solution replacing andesitic volcanic and pyroclastic rocks. Tinticite is the later product than them. In weathered surface of the ore, masses of tinticite become partially loose or is veined by goethite due to loss of phosphorus.
