James L Sharpe

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

Abstract 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 hardness of 1½; 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 C4H7.89O5.07Cu1.00Fe0.01. The simplified formula is C4H8O5Cu or Cu(CH3COO)2. H2O, 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, α = 13.162(3), b = 8.555(2), c = 13.850(3) Å, β = 117.08(3)°, Z = 8. The density, calculated from single-crystal data, is 1.910 g cm-3. The strongest lines in the X-ray powder pattern are [dobs (Iobs) (hkl)] 6.921 (100) (011); 3.532 (28) (202); 6.176 (14) (200); 3.592 (11) (1̅22); 5.382 (10) (2̅11); 2.278 (10) (204); 5.872 (9) (002). Hoganite (orientation presently unknown) is biaxial positive with α = 1.533(2), β = 1.541(3), γ = 1.554(2), 2V(meas.) = 85(5)°, 2V(calc.) = 76.8°, dispersion is r < v, medium (white light); it is strongly pleochroic with X = blue, Y = pale bluish, Z = pale bluish green and absorption X > Y > 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 1½; 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 C8H23.77O14.23Ca1.02-Cu1.00. The simplified formula is C8H24O14CaCu or CaCu(CH3COO)4. 6H2O, 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, α = 11.155(4), c = 16.236(17) Å, Z = 4. The density, calculated from refined cell data, is 1.472 g cm-3. The strongest lines in the X-ray powder pattern are [dobs (Iobs) (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 ω = 1.439(2) and ε = 1.482(3) (white light); pleochroism is bluish with a greenish tint (O), pale bluish with a greyish tint (E), and absorption O ≥ 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.

Secondary Copper Minerals: from Eastern Australia

Copper mining in the colony of New South Wales commenced prior to 1845 (Carne 1908), and prospects and mines are widely distributed in what became the state of the same name (Markham and Basden 1974). Copper mining remains extremely active, but very few deposits had not been at least prospected prior to 1900. The Cu-Au orebodies at Goonumbla are notable exceptions (Heithersay et al. 1990). Copper was discovered at Cobar in central west New South Wales in 1869. Three well sinkers traveling south from Bourke camped near where green and blue stains were showing in exposed rocks. They collected samples and in their travels showed them to an innkeeper’s wife, who had been a bal gal (woman who worked in a mine) in Cornwall. She identified the specimens as containing copper. The men purchased a mineral concession over the site, and leases were later amalgamated to form the Great Cobar Copper Mining Company. Although the field was hampered by a shortage of water, Cobar thrived, and several other major mines were established (Stegman and Stegman 2002). Currently, there are three major mines operating near Cobar—the CSA, the Peak (also mining the New Occidental and New Cobar lodes), and the Endeavor (Elura)—all of which mine sulfides underground. From 1870 to 1890 numerous mines opened in the surrounding region. More important copper mines were at Nymagee, Mount Hope, Tottenham, Mineral Hill, and Girilambone. Most other copper deposits in New South Wales are relatively small. Aside from Goonumbla, the only other major producer is Newcrest at Cadia, near Orange (Newcrest Mining Staff 1998). Mining in what became the state of Queensland began somewhat later than in New South Wales. Copper in the Mount Isa Block, in northwestern Queensland, was first discovered in 1867 by Ernest Henry, who established the Great Australia mine at Cloncurry. Aborigines led him to other locations where they had seen green malachite stains. These became the Blockade and Mount Oxide mines (Blainey 1970). Soon after, two other significant mines were established at Mount Elliott and Kuridala. In following years prospectors located numerous copper deposits in Secondary Copper Minerals