Antipinite, KNa₃Cu₂(C₂O₄)₄, a new mineral species from a guano deposit at Pabellón de Pica, Chile

Abstract

The new oxalate mineral antipinite is found in a guano deposit located on the Pabellón de Pica Mountain, Iquique Province, Tarapacá Region, Chile. Associated minerals are halite, salammoniac, chanabayaite, joanneumite and clays. Antipinite occurs as blue, imperfect, short prismatic crystals up to 0.1 mm × 0.1 mm × 0.15 mm in size, as well as their clusters and random aggregates. The mineral is brittle. Mohs hardness is 2; Dmeas = 2.53(3), Dcalc = 2.549 g cm–3. The infrared spectrum shows the presence of oxalate anions and the absence of absorptions associated with H2O molecules, C–H bonds, CO32–, NO3– and OH– ions. Antipinite is optically biaxial (+), α = 1.432(3), β = 1.530(1), γ = 1.698(5), 2Vmeas = 75(10)°, 2Vcalc = 82°. The chemical composition (electron-microprobe data, C measured by gas chromatography of products of ignition at 1200°C, wt.%) is Na2O 15.95, K2O 5.65, CuO 27.34, C2O3 48.64, total 99.58. The empirical formula is K0.96Na3.04Cu2.03(C2.00O4)4 and the idealized formula is KNa3Cu2(C2O4)4. The crystal structure was solved and refined to R = 0.033 based upon 4085 unique reflections with I > 2σ(I). Antipinite is triclinic, space group P1, a = 7.1574(5), b = 10.7099(8), c = 11.1320(8) Å, α = 113.093(1), β = 101.294(1), γ = 90.335 (1)°, V = 766.51(3) Å3, Z = 2. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I,%) (hkl)] are 5.22 (40) (111), 3.47 (100) (032), 3.39 (80) (210), 3.01 (30) (033, 220), 2.543 (40) (122, 034, 104), 2.481 (30) (213), 2.315 (30) (143, 310), 1.629 (30) (146, 414, 243, 160).

Middlebackite, a new Cu oxalate mineral from Iron Monarch, South Australia: Description and crystal structure

“…Middlebackite is the second Cu oxalate mineral after moolooite, CuC 2 O 4 , (Clarke and Williams, 1986; Christensen et al ., 2014). Other Cu-bearing oxalates known in nature are antipinite, KNa 3 Cu 2 (C 2 O 4 ) 4 , (Chukanov et al ., 2015) and wheatleyite, Na 2 Cu(C 2 O 4 ) 2 ·2H 2 O (Rouse et al . 1986).…”

“…The Cu oxalate minerals moolooite and antipinite from their type localities were produced by the interaction of oxalic acids from guano with copper sulfide minerals (Clarke and Williams 1986; Chukanov et al ., 2015). The area in the Iron Monarch quarry that was most likely the source of the boulder that contained middlebackite was mined out many years ago (Francis, 2010) and the source of oxalate is not known for certain.…”

Fiemmeite Cu2(C2O4)(OH)2∙2H2O, a New Mineral from Val di Fiemme, Trentino, Italy

“…Other copper(II) oxalates with additional cations are wheatleyite Na2Cu(C2O4)2•2H2O [16] and antipinite KNa3Cu2(C2O4)4 [17].…”

Ammoniotinsleyite, (NH4)Al2(PO4)2(OH)⋅2H2O, a new mineral species from the guano deposit at Pabellón de Pica, Iquique Province, Chile

“…The guano deposit situated on Pabellón de Pica Mountain, 1.5 km south of Chanabaya village, Iquique Province, Tarapacá Region, Chile (20°55’S, 70°08’W) belongs to the famous belt of guano occurrences of the Atacama Desert stretching along the northern coast of Chile (Ericksen, 1981; Pankhurst and Herve, 2007; Appelton and Nothold, 2002; Bojar et al ., 2010). Pabellón de Pica is one of the most interesting mineralogical occurrences in this area being the type locality of several nitrogen-bearing and organic minerals: ammineite, CuCl 2 (NH 3 ) 2 (Bojar et al ., 2010), joanneumite, Cu(C 3 N 3 O 3 H 2 ) 2 (NH 3 ) 2 (Bojar et al ., 2017), chanabayaite, Cu 4 (N 3 C 2 H 2 ) 4 (NH 3 ) 4 Cl 2 (Cl,OH) 2 ⋅H 2 O (Chukanov et al ., 2015a), shilovite, Cu(NH 3 ) 4 (NO 3 ) 2 (Chukanov et al ., 2015b), antipinite, KNa 3 Cu 2 (C 2 O 4 ) 4 (Chukanov et al ., 2015c), möhnite, (NH 4 )K 2 Na(SO 4 ) 2 (Chukanov et al ., 2015d) and triazolite, NaCu 2 (N 3 C 2 H 2 ) 2 (NH 3 ) 2 Cl 3 ⋅4H 2 O (Chukanov et al ., 2018).…”