Barlowite, Cu 4FBr(OH) 6, a new mineral isotructural with claringbullite: Description and crystal structure

P Elliott, Mark Cooper, Allan Pring

    Research output: Contribution to journalArticle

    16 Citations (Scopus)

    Abstract

    The new mineral species barlowite, ideally Cu4FBr(OH)6, has been found at the Great Australia mine, Cloncurry, Queensland, Australia. It is the Br and F analogue of claringbullite. Barlowite forms thin blue, platy, hexagonal crystals up to 0.5 mm wide in a cuprite-quartz-goethite matrix associated with gerhardtite and brochantite. Crystals are transparent to translucent with a vitreous lustre. The streak is sky blue. The Mohs hardness is 2-2.5. The tenacity is brittle, the fracture is irregular and there is one perfect cleavage on {001}. Density could not be measured; the mineral sinks in the heaviest liquid available, diluted Clerici solution (D ≈ 3.8 g/cm3). The density calculated from the empirical formula is 4.21 g/cm3. Crystals are readily soluble in cold dilute HCl. The mineral is optically non-pleochroic and uniaxial (-). The following optical constants measured in white light vary slightly suggesting a small variation in the proportions of F, Cl and Br: ω 1.840(4)-1.845(4) and ε 1.833(4)-1.840(4). The empirical formula, calculated on the basis of 18 oxygen atoms and H2O calculated to achieve 8 anions and charge balance, is Cu4.00F1.11Br0.95Cl0.09(OH)5.85. Barlowite is hexagonal, space group P63/mmc, a = 6.6786(2), c = 9.2744(3) Å, V = 358.251(19) Å3, Z = 2. The five strongest lines in the powder X-ray diffraction pattern are [d(Å)(I)(hkl)]: 5.790(100)(010); 2.889(40)(020); 2.707(55)(112); 2.452(40)(022); 1.668(30)(220).

    Original languageEnglish
    Pages (from-to)1755-1762
    Number of pages8
    JournalMineralogical Magazine
    Volume78
    Issue number7
    DOIs
    Publication statusPublished - 2014

    Keywords

    • Barlowite
    • copper bromide fluoride
    • crystal structure
    • Great Australia Mine
    • new mineral species

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