New data on supergene minerals from the Rainer mining field, Ľubietová - Podlipa deposit (Slovak Republic)

An interesting supergene mineral association with bismutite, Bi and Cu-rich corkite and kintoreite, mrázekite and petitjeanite was recently identified at the Rainer mining field, Ľubietová-Podlipa copper deposit near Banská Bystrica, Slovak Republic. Bismutite is common mineral in studied samples and it occurs as yellowish-green to pale yellow, powdery to earthy aggregates up to 6 x 1.5 cm in size, which are embedded in quartz and represent pseudomorphs after accumulations of preexisting Cu-Bi or Cu-Pb-Bi sulfosalts. It was identified by PXRD and its refined unit-cell parameters (for the orthorhombic space group Imm2) are: a 3.873(2), b 3.874(4) Å, c 13.722(9) Å and V 205.9(3) Å3. Corkite forms yellowish-green, irregular to hemispherical aggregates up to 1 mm in size, which consists of well-developed rhombohedral crystals up to 30 μm. It is associated with bismutite, mrázekite, goethite, malachite and pseudomalachite. The unit-cell parameters of corkite refined from the powder X-ray diffraction data (for the trigonal space group R-3m) are: a 7.277(8), c 16.740(6) Å with V 768.8(1) Å3. Its chemical composition is distinctive by unusually high concentrations of Bi (up to 0.28 apfu) and Cu (up to 1.06 apfu), with the average (n=19) empirical formula corresponding to (Pb0.88Bi0.16)Σ1. 04 (Fe2.42Cu0.72Al0.05)Σ3. 19[(PO4)0.99(SO4)0.77(PO3OH)0.23(AsO4)0.01]Σ2. 00(OH)6.10 on the basis of P+As+S+Si = 2 apfu. Kintoreite occurs as greenish-yellow, fine crystalline coatings, which cover areas up to 2 x 2 cm, in association with mrázekite, bismutite, petitjeanite, pseudomalachite and goethite. The unit-cell parameters of kintoreite refined from the powder X-ray diffraction data (for the trigonal space group R-3m) are: a 7.285(8), c 16.883(5) Å with V 776(1) Å3. It contain elevated amounts of Bi (up to 0.10 apfu) and Cu (up to 0.22 apfu) and its average (n=6) empirical formula can be expressed as (Pb0.93Bi0.08K0.04Ca0.01)Σ1.06(Fe2.48Al0.34Cu0.14)Σ2. 96[(PO3OH)1.00(PO4)0.81(SiO4)0.16(SO4)0.02(AsO4)0.01]Σ2. 00(OH)5.73 on the basis P+As+S+Si = 2 apfu. Mrázekite is relatively abundant in studied samples and it is often closely associated with bismutite. It occurs as cerulean-blue crusts, hemispherical or irregular crystalline aggregates. Radial aggregates of well-developed acicular to thin-tabular crystals of mrázekite are infrequent. The unit-cell parameters of mrázekite refined from the powder X-ray diffraction data (for the monoclinic space group P21/m) are: a 9.067(5), b 6.341(4), c 21.252(9) Å, β 101.64(4)° with V 1197(1) Å3. Its average (n = 8) empirical formula is (Bi1.95Pb0.02)Σ1. 97(Cu2.91Fe0.02Al0.01)Σ2. 94[(PO4)1.99 (AsO4)0.01]Σ2. 00O2.00(OH)1.78·2H2O based on P+As = 2 apfu. Petitjeanite is very rare and it forms microscopic, irregular aggregates and crusts up to 200 μm associated with goethite, pseudomalachite, mrázekite and kintoreite. It was confirmed by EPMA-WDS and its average (n = 4) empirical formula can be expressed as (Bi2.67Pb0.16Al0.08Fe0.05K0.03Cu0.03Ca0.02)Σ3. 04 [(PO4)1.84(SiO4)0.09(AsO4)0.07]Σ2. 00O1.00(OH)0.72 on the basis P+As+Si = 2 apfu.