Domitrovicite, Zn(C2H3O3)2(H2O)2, AND PUSCHRIDGEITE, Mn(C2H3O3)2(H2O)2, TWO NEW GLYCOLATE MINERALS FROM THE SANTA CATALINA MOUNTAINS, TUCSON, ARIZONA, USA

Two new organic minerals, domitrovicite and puschridgeite, ideally Zn(C2H3O3)2(H2O)2 and Mn2+(C2H3O3)2(H2O)2, respectively, were discovered from the western end of Pusch Ridge in the Santa Catalina Mountains, north of Tucson, Arizona, USA. Both minerals occur as bladed or prismatic crystals. Minerals associated with domitrovicite include stanevansite, chrysocolla, rasmussenite, and quartz, whereas those associated with puschridgeite include baryte, fluorite, hematite, jarosite, quartz, and rasmussenite. Both minerals are colorless in transmitted light, transparent with a white streak and vitreous luster. They are brittle and have a Mohs hardness of ∼1½; cleavage is perfect on {100}. The measured and calculated densities are 1.82(5) and 1.87 g/cm3, respectively, for domitrovicite and 1.74(3) and 1.77 g/cm3 for puschridgeite. Optically, both minerals are biaxial (−), with α = 1.476(2), β = 1.544(2), γ = 1.547(2), 2Vmeas. = 21(3)°, 2Vcal. = 22.0° for domitrovicite and α = 1.467(2), β = 1.535(2), γ = 1.542(2), 2Vmeas. = 34(2)°, 2Vcal. = 34.3° for puschridgeite. Electron microprobe analyses, together with an elemental combustion analysis for C and H measurements for puschridgeite, yielded an empirical formula (based on 8 O apfu) of (Zn0.64Mg0.34)Σ0.98(C2H3O3)2(H2O)2 for domitrovicite and (Mn0.68Mg0.31)Σ0.99(C1.98H2.95O3)2(H2O)2 for puschridgeite, which can be simplified as (Zn,Mg)(C2H3O3)2(H2O)2 and (Mn,Mg)(C2H3O3)2(H2O)2, respectively. The strongest powder X-ray diffraction lines are [d (Å) (I%, hkl)] 5.36 (100, 102), 4.79 (43, 111), 3.827 (28, 300), 3.082 (48, 311), and 2.009 (20, 421) for domitrovicite and 5.620 (43, 1¯02), 5.347 (100, 102), 4.832 (50, 111), 3.880 (36, 300), and 3.121 (59, 004/311) for puschridgeite. Domitrovicite and puschridgeite are the natural counterparts of synthetic bis(glycolato)zinc(II) dihydrate and bis(glycolato)Mn(II) dihydrate, respectively. Both minerals are isotypic with stanevansite, Mg(C2H3O3)2(H2O)2, and synthetic Co2+(C2H3O3)2(H2O)2, being monoclinic with space group P21/c. The unit-cell parameters are a = 11.4394(6), b = 5.8625(3), c = 12.5065(7) Å, β = 91.256(3)°, and V = 838.53(8) Å3 for domitrovicite and a = 11.6137(5), b = 5.9139(3), c = 12.5694(6) Å, β = 92.112(2)°, and V = 862.71(7) Å3 for puschridgeite. Their structures are characterized by the mononuclear complex [M2+(C2H3O3)2(H2O)2] (M = Zn, Mn, Mg), which is connected to one another by hydrogen bonds to form a three-dimensional supramolecular architecture. Each M cation is octahedrally coordinated by two chelating glycolate ligands and two H2O molecules. Domitrovicite and puschridgeite are among ten glycolate minerals documented thus far. Their discoveries imply that a wide range of solid solutions may exist in the M2+(C2H3O3)2(H2O)2-type compounds and glycolate minerals might be widespread in nature, serving as a potential reservoir for biologically fixed carbon.