SLAVKOVITE, Cu13(AsO4)6(AsO3OH)4{middle dot}23H2O, A NEW MINERAL SPECIES FROM HORNI SLAVKOV AND JACHYMOV, CZECH REPUBLIC: DESCRIPTION AND CRYSTAL-STRUCTURE DETERMINATION

Abstract

Slavkovite, Cu 13 (AsO 4 ) 6 (AsO 3 OH) 4 •23H 2 O, is a newly discovered supergene mineral from the Geschieber vein, Svornost mine at the Jáchymov (St. Joachimsthal) ore district, Czech Republic, commonly associated with lavendulan, geminite, lindackerite and ondrušite. It forms coatings of pale green rosettes up to 1 mm across or individual spherical aggregates up to 5 mm across. Individual acicular to lath-like crystals are up to 1 mm long and 0.05 mm thick, and are colorless with a greenish tint. Slavkovite is pale green, translucent (aggregates) to colorless with a greenish tint, transparent (crystals). It has a white streak and a vitreous luster, and does not fluoresce under both short-and long-wave ultraviolet light. The cleavage on {011} is perfect, and on {010}, it is good. The Mohs hardness is ~3.5-4; slavkovite is very brittle, with an irregular fracture. Its measured density, 3.05(1) g/cm 3 , is identical to the calculated one. Slavkovite is biaxial positive; the indices of refraction are a' 1.591(2), b' 1.620(2), g' 1.701(2), and the 2V (calc.) is approximately 64°. It is moderately pleochroic (X light gray to colorless, Y very light greenish gray, Z light green). Slavkovite is triclinic, space group P1, a 6.408 (3), b 14.491(5), c 16.505(8) Å, a 102.87(3), b 101.32(5), g 97.13(3)°, V 1442(1) Å 3 , Z = 1, a:b:c = 0.4422:1:1.1390. The strongest eight lines in the X-ray powderdiffraction pattern [d in Å(I)(hkl)] are as follows: 15.70(3)(001), 11.98(100)(011), 6.992(3)(021, 020), 5.992(6)(022), 3.448(5) (040), 2.967(5)(035), 2.4069(4)(154), 2.4002(4)(115, 135, 046, 062). The chemical analyses made with an electron microprobe yielded FeO 0.12, CuO 39.93, Al 2 O 3 0.13, As 2 O 5 44.71, H 2 O 17.31, total 102.20 wt.%. The resulting empirical formula on the basis of 63(O, OH, H 2 O) anions is (Cu 12.96 Al 0.07 Fe 0.04 ) S13.07 (AsO 4 ) 6.11 (AsO 3 OH) 3.93 •22.83H 2 O. The ideal end-member formula, Cu 13 (AsO 4 ) 6 (AsO 3 OH) 4 •23 H 2 O, requires CuO 39.26, As 2 O 5 43.36, H 2 O 17.10, total 100.00 wt. %. The crystal structure of slavkovite has been solved by direct method and refined to a final R obs of 4.37% on the basis of 6613 observed reflections collected on a single-crystal diffractometer with MoKa X-radiation. The crystal structure is based upon sheets consisting of copper polyhedra linked by arsenate and hydrogen arsenate tetrahedra. The sheets are linked by bridging Cu6-F polyhedra. In §

Thermodynamic properties, crystal structure and phase relations of pushcharovskite [Cu(AsO<sub>3</sub>OH)(H<sub>2</sub>O) ⋅ 0.5H<sub>2</sub>O], geminite [Cu(AsO<sub>3</sub>OH)(H<sub>2</sub>O)] and liroconite [Cu<sub>2</sub>Al(AsO<sub>4</sub>)(OH)<sub>4</sub> ⋅ 4H<sub>2&

“…Geminite is undersaturated (SI −5.2) in the acidic droplets but approaches saturation as more As is oxidized or the solutions leach additional Cu from the primary ores. The dissolution reaction of geminite under acidic conditions is (Sarp andČerný, 1998), and for the lindackerite group ACu 4 (AsO 4 ) 2 (AsO 3 OH) 2 • 9H 2 O, where A = Cu, Zn, Co, Ca, Ni, Mg, with lindackerite (Vogl, 1853), ondrušite (Sejkora et al, 2011), hloušekite (Plášil et al, 2014) and veselovskýite (Sejkora et al, 2010b) having their type locality in Jáchymov (see Škácha et al, 2019, for more information). From its type locality in the Salsigne mine (France, Sarp andČerný, 1998), yvonite was described in association with geminite, lindackerite and pushcharovskite.…”

Thermodynamics of the Cu, Zn, and Cu-Zn phases: zincolivenite, adamite, olivenite, ludjibaite, strashimirite, and slavkovite

“…The samples of slavkovite come from the holotype specimen from Jáchymov used to describe this mineral, deposited in the Mineralogical collection of the National Museum in Prague with the sample label P1N 83.038. They were described by Sejkora et al (2010) and an overview of that description was provided above.…”

“…Slavkovite [ideally Cu 13 (AsO 4 ) 6 (AsO 3 OH) 4 •23H 2 O] was described by Sejkora et al (2010) from the Geschieber vein in Jáchymov, Czech Republic. It is a weathering product of chalcopyrite and tennantite and occurs together with geminite [Cu(AsO 3 OH)•H 2 O], lindackerite [CuCu 4 (AsO 4 ) 2 (AsO 3 OH) 2 •9H 2 O], ondrušite [CaCu 4 (AsO 4 ) 2 (AsO 3 OH) 2 •10H 2 O] and an unnamed lavendulan-like mineral phase of an idealized composition Ca 2 Cu 5 (AsO 4 ) 4 (OH,Cl) Sejkora et al (2010) mentioned another site for this mineral, in Krásno, near Horní Slavkov (also Czech Republic), where it formed by weathering of tennantite and cuprite. Slavkovite is associated with clay minerals and X-ray amorphous Cu-Fe arsenates.…”

Krupičkaite, Cu6[AsO3(OH)]6·8H2O, a new copper arsenate mineral from Jáchymov (Czech Republic)

“…More generally, krupičkaite is related to several other layered copper arsenate minerals initially found in the Jáchymov ore district. Some of them possess the same, or close, As/Cu ratio of the As-Cu layers such as slavkovite (Sejkora et al 2010c), other minerals of the lindackerite supergroup (Sejkora et al 2011;Plášil et al 2014a, b), or yvonite (Sarp and Černý 1998) among others (Tab. 6).…”