gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1982.046.340.09 Dwornikite, (Ni,Fe)SO4 · H2O, a Member of the Kieserite Group from Minasragra, Peru Milton Charles US Geological Survey and George Washington University Evans Howard T.Jr. Johnson Robert G. US Geological Survey, National Center 959, Reston, Virginia 22092, USA 9 1982 46 340 351 355 28 9 1981 Copyright © 1982, The Mineralogical Society 1982 Abstract

Dwornikite, (Ni1−xFex)SO4 · H2O is a member of the kieserite group, monoclinic with space group C2/c. Specimens from Minasragra, Peru with x ∼ 0.1 have a unit cell with a = 6.839(2), b = 7.582(2), c = 7.474(2) Å, and β = 117.85(2)°. The six strongest lines of the powder pattern are: 3.342 (1¯12, 100), 4.732 (110, 70), 3.024 (200, 70), 4.754 (1¯11, 50), 3.293 (021, 35), 2.491 (022, 35). The mineral occurs as fine grained white aggregates associated with vanadium sulphide ores containing patronite and bravoite, mixed with other oxidation products. New unit cell data for the synthetic end-member compounds NiSO4 · H2O and FeSO4 · H2O, and new X-ray powder data for retgersite (NiSO4 · 6H2O) are provided.