Epifanovite, NaCaCu5(PO4)4lAsO2(OH)2] ∙ 7H2O a new mineral from the Kester deposit (Sakha-Yakutia, Russia)
Yakovenchuk V. N., Pakhomovsky Ya. A., Konoplyova N. G., Panikorovskii T. L., Mikhailova Yu. A., Bocharov V. N., Krivovichev S. V., Ivanyuk G. Yu.
Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2017. V. 146. N 3. P. 30-39
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Language: Russian
Abstract
Epifanovite, NaCaCu5(PO4)4[AsO2(OH)2]∙ 7H2O, is a new natural arsenate-phosphate of copper, sodium and calcium. It was found in a quartz-phosphate nest within greisenized cassiterite-rich granodiorite of the Kester tin deposit (Sakha-Yakutia, Russia). Mineral occurs as crusts of tabular pseudotetragonal crystals up to 50 μm across and 10 μm thick. Associated minerals are fluorapatite, pseudo malachite, slavkovite, tobermorite, libethenite, arsenolite, native copper and unknown Mg-Zn phosphate. Epifanovite has a turquoise-blue color and pale blue streak. Luster is vitreous (dull in crusts). Mohs’ hardness is 3. Brittle. Cleavage is perfect on (001) and good on (100) and (010). Density measured in Clerichi solution is 3.65(3) g/cm–3, the calculated density is 3.73 g/cm–3. Optically biaxial (–), α = 1.708(5), β = 1.730(5), γ = 1.735(5). 2Vmeas = 40—45°, 2Vcalc. = 50°. Optical orientation: X = a, Y = b. Empirical formula calculated on the basis of P + As = 5 is (Na0.94K0.06)∑1.00 (Ca0.82Na0.08)∑0.90(Cu5.04Zn0.06)∑5.10(PO4)4[(As0.81P0.19)∑1.00(O1.92OH2.06Cl0.02)∑4.00] 7.37H2O. The idealized formula is NaCaCu5(PO4)4[AsO2(OH)2]∙ 7H2O. The Raman spectrum contain following lines: 293, 359 (ν1—2, CuO5); 455, 556, 594, 640, 921, 962, 1002, 1086, 1153 (ν1—4 PO4), 77, 121, 161, 183, 730, 828, 858 (ν1—3 AsO4), 2900, 3200, 3410 (ν1, OH) cm–1. The mineral is monoclinic, P21/m, a = 9.6912(9), b = 9.7440(9), c = 9.9561(9) Å, β = 102.23 (1)°, V = 918.7(1) Å3, Z = 2. Eight strongest lines in the powder X-ray diffraction pattern are (I—d[Å]-hkl): 100—9.73—001; 35—6.79—110; 12—4.355—021; 43—3.072—130; 24—3.061—221; 24—3.003—2 22; 11—2.698—023; 10—1.6775—504. The mineral is named in honor of the Russian geologist P.P. Epifanov, the discoverer of the Ege-Khaya and Kester tin deposits. Epifanovite is structurally close to lavendulan-group minerals and related species: andyrobertsite, calcioandyrobertsite, mahnertite and richelsdorfite.
Key words: epifanovite, new mineral, copper phosphate-arsenate, Kester deposit, Sakha-Yakutia.
