Hoganite and paceite : two new acetate minerals from the Potosi mine, Broken Hill, Australia

Hoganite, copper(II) acetate monohydrate, and paceite (pronounced "pace-ite"), calcium(II) copper(II) tetraacetate hexahydrate, occur as isolated crystals embedded in ferruginous gossan from the Potosi Pit, Broken Hill, New South Wales, Australia. They are associated with goethite, hematite, quartz, linarite, malachite, azurite, cerussite and cuprian smithsonite. Hoganite is bluish green with a pale blue streak and a Mohs a hardness of 1 1/2; it possesses perfect {001} and distinct {110} cleavages and has a conchoidal fracture. Chemical analysis of hoganite gave (wt.%) C 23.85; H 3.95; Cu 31.6; Fe 0.4; O (by difference) 40.2, yielding an empirical formula of C â‚„ H (sub 7.89) O (sub 5.07) Cu (sub 1.00) Fe (sub 0.01) . The simplified formula is C â‚„ H â‚Ë"  O â‚… Cu or Cu(CH â‚Æ' COO) 2 .H â‚‚ O, the mineral being identical to the synthetic compound of the same formula. Single-crystal X-ray data for hoganite are: monoclinic, space group C2/c, a = 13.162(3), b = 8.555(2), c = 13.850(3) Aa, beta = 117.08(3) degrees , Z = 8. The density, calculated from single-crystal data, is 1.910 g cm (super -3) . The strongest lines in the X-ray powder pattern are [d obs (I obs ) (hkl)] 6.921 (100) (011); 3.532 (28) (202); 6.176 (14) (200); 3.592 (11) (122); 5.382 (10) (211); 2.278 (10) (204); 5.872 (9) (002). Hoganite (orientation presently unknown) is biaxial positive with alpha = 1.533(2), beta = 1.541(3), gamma = 1.554(2), 2V(meas.) = 85(5) degrees , 2V(calc.) = 76.8 degrees , dispersion is rY>Z. The mineral is named after Graham P. Hogan of Broken Hill, New South Wales, Australia, a miner and well-known collector of Broken Hill minerals. Paceite is dark blue with a pale blue streak and a Mohs hardness of 1 1/2; it possesses perfect {100} and {110} cleavages and has an uneven fracture. Chemical analysis of paceite gave (wt.%) C 21.25; H 5.3; Ca 9.0; Cu 14.1; O (by difference) 50.35, yielding an empirical formula of C â‚Ë"  H (sub 23.77) O (sub 14.23) Ca (sub 1.02) Cu (sub 1.00) . The simplified formula is C â‚Ë"  H â‚‚â‚„ O â‚ÂÂâ‚„ CaCu or CaCu(CH â‚Æ' COO) â‚„ .6H â‚‚ O, the mineral being identical to the synthetic compound of the same formula. Unit-cell data (refined from X-ray powder diffraction data) for paceite are: tetragonal, space group I4/m, a = 11.155(4), c = 16.236(17) Aa, Z = 4. The density, calculated from refined cell data, is 1.472 g cm (super -3) . The strongest lines in the X-ray powder pattern are [d obs (I obs ) (hkl)] 7.896 (100) (110); 3.530 (20) (310); 5.586 (15) (200); 8.132 (8) (002); 9.297 (6) (101); 2.497 (4) (420); 3.042 (3) (321). Paceite is uniaxial positive with omega = 1.439(2) and epsilon = 1.482(3) (white light); pleochroism is bluish with a greenish tint (O), pale bluish with a greyish tint (E), and absorption O> or =E. The mineral is named after Frank L. Pace of Broken Hill, New South Wales, Australia, an ex-miner and well-known collector of Broken Hill minerals.