Redefinition of theresemagnanite, NaCo4(SO4)(OH)6Cl·6H2O; new data and relationship to 'cobaltogordaite'

Theresemagnanite was originally described from the Cap Garonne mine, Var, France. Its ideal formula was reported as (Co,Zn,Ni)6(SO4)(OH,Cl)10·8H2O; without crystal structure data, only the powder X-ray diffraction pattern was given. Revision of the holotype material revealed that theresemagnanite is identical to 'cobaltogordaite' (IMA2014-043), recently described from the Blue Lizard mine, Utah, USA. Theresemagnanite is thus redefined in accordance with the new data obtained for the neotype specimen from Blue Lizard (formerly the holotype specimen of 'cobaltogordaite') and 'cobaltogordaite' has been discredited by the International Mineralogical Association Commission on New Mineral Nomenclature and Classification (IMA CNMNC). Theresemagnanite has the ideal, end-member formula NaCo4(SO4)(OH)6Cl·6H2O. The empirical formulae of the holotype (Cap Garonne) and the neotype (Blue Lizard), both based on microprobe analyses and calculated on the basis of 17 O + Cl atoms per formula unit (with fixed 6 OH groups and 6 H2O molecules; H content is calculated by stoichiometry) are (Na0.64K0.09)Σ0.73(Co2.35Zn1.22Ni0.50)Σ4.07S1.02O3. 98(OH)6 Cl1.02·6H2O and Na1.01(Co1.90Zn1.37Ni0.48Cu0.15Mn0.05)Σ3.95S1.03O4.09 (OH)6Cl 0.91·6H2O, respectively. Theresemagnanite is trigonal, P3 $, a = 8.349(3), c = 13.031(2) Å, V = 786.6(4) Å3 and Z = 2 (neotype). The strongest powder X-ray diffraction lines are [dobs in Å (hkl) (Irel)]: 13.10 (001)(100), 6.53 (002)(8), 4.173 (110)(4), 3.517 (112)(5), 2.975 (104, 104)(4), 2.676 (211)(5) and 2.520 (122)(5) (neotype). Theresemagnanite is a cobalt analogue of gordaite, NaZn4(SO4)(OH)6Cl·6H2O. These minerals represent the gordaite group, accepted by the IMA CNMNC.