Crystal structure refinement of aurichalcite, (Cu, Zn)5(CO3)2(OH)6, from the Lavrion Mining District, Greece

High-Pressure Experimental and DFT Structural Studies of Aurichalcite Mineral

“…Quantitative chemical analyses indicate that the Zn 3.78(2) Cu 1.22(2) (CO 3 ) 2 (OH) 6 chemical composition is quite uniform through the sample. From XRD measurements, we obtained the lattice parameters of aurichalcite: a = 13.809 (7) Å, b = 6.412(2) Å, c = 5.315(3) Å, β = 100.74(5) • (V = 462.3(3) Å 3 ), which are in good agreement with those previously reported in the literature [23,24]. Unfortunately, the sample is not perfectly homogeneous and does not correspond to a randomly oriented powder.…”

“…Each of these sheets is composed of double layers of close-packed O atoms that contain metal atoms in two slightly different octahedral coordination environments. According to previous single-crystal XRD results [23], four Zn/Cu atoms per unit-cell are located in tetragonally Jahn-Teller distorted octahedral sites with four short metal-oxygen distances (2 × 1.98 Å + 2 × 2.01 Å) and two long distances (2 × 2.33 Å), whereas two Zn/Cu atoms per unit-cell are centering other octahedra with a smaller range of metal-oxygen distances (1.98-2.21 Å). Diffraction and especially spectroscopic results suggest that the Cu atoms preferentially occupy the first of these octahedral types, which are connected by common edges forming chains along the b axis.…”

“…Aurichalcite (Zn,Cu) 5 (CO 3 ) 2 (OH) 6 , in which carbonate and hydroxyl groups coexist, is a naturally-occurring mineral commonly found in association with hemimorphite Zn 4 (Si 2 O 7 )(OH) 2 •H 2 O and other basic carbonates such as hydrozincite Zn 5 (CO 3 ) 2 (OH) 6 , rosasite (Zn,Cu) 2 (CO 3 )(OH) 2 , malachite Cu 2 (CO 3 )(OH) 2 or azurite Cu 3 (CO 3 ) 2 (OH) 2 in oxidized zones of zinc and copper deposits. The Zn:Cu ratio in natural aurichalcite samples is known to vary between 5:1 zinc-rich composition and 4:5 [23]. Aurichalcite is also important as a synthetically produced intermediate in the preparation of copper/zinc oxide catalysts for a variety of industrial hydrogenation processes, such as methanol production [24,25].…”

“…At room conditions, aurichalcite is monoclinic, space group P2 1 /m, with lattice parameters a = 13.82(2) Å, b = 6.419(3) Å, c = 5.29(3) Å, β = 101.04(2) • (V = 461(3) Å 3 , Z = 2) for the chemical composition Zn 3 Cu 2 (CO 3 ) 2 (OH) 6 [24]. The crystal structure of an aurichalcite specimen with a different composition, Zn 2.3 Cu 2.7 (CO 3 ) 2 (OH) 6 , was later refined [23] with comparable unit-cell parameters. The structure consists of complex layers of cation-centered polyhedra in which the Zn and Cu atoms are in four coordination environments: two octahedral sites with different distortion, a trigonal bipyramidal site and a tetrahedral site (described in detail later).…”

Voudourisite, Cd(SO4)·H2O, and lazaridisite, Cd3(SO4)3·8H2O, two new minerals from the Lavrion Mining District, Greece

“…The area is also well-known for the occurrence of (up to now) ~580 mineral species, and it is the type locality of ~20 new minerals (Rieck et al , 2018). The district has been the subject of intense investigation by the authors for more than two decades (Rieck, 1999; Rieck and Rieck, 1999; Rieck and Wendel, 1999; Wendel and Rieck, 1999 a , b ; Giester et al , 2000; Giester et al , 2007; Rieck, 2012; Giester and Rieck, 2014; Kolitsch et al , 2014 a , b ; Kolitsch et al , 2015). Several new mineral species have been described by our research group, i.e.…”