The supergene mineral association with brandholzite from Pernek, Malé Karpaty Mountains, Slovak Republic

Abstract

Brandholzite, a hydrated hydroxide of Mg 2+ and Sb 5+, was found at the Krížnica deposit near Pernek (Malé Karpaty Mountains, Slovak Republic); it is the third occurrence of this mineral phase worldwide. Crystals and crusts of brand holzite occur as surface coatings on altered shales mineralized with stibnite and pyrite. Associated minerals include roméitelike phases, sulphur, aragonite, gypsum, sénarmontite and Sbrich Fehydroxides. Brandholzite forms euhedral tabular crystals of hexagonal habit, typically 0.5 to 0.8 mm across, exceptionally up to 2 mm long. 6 ] 2.00 . The XRD pattern was indexed in a trigonal setting (space group P3), with refined unitcell parameters a = 16.1076(9), c = 9.8628(9) Å and V = 2216.1(2) Å 3 . The thermogravimetric curve shows total weight loss of 34.6 wt. % (over the interval of 20-800 °C), caused by H 2 O release. The initial rapid weight decrease (20-140 °C) was followed by a minor continuous weight loss up to 800 °C. Brandholzite from Pernek and its mineral association were probably formed by subrecent weathering processes in an abandoned mines environment.

A Raman spectroscopic study of bukovskýite Fe2(AsO4)(SO4)(OH)· 7H2O, a mineral phase with a significant role in arsenic migration

“…As a part of our ongoing research into supergene mineral formation,18, 19 this paper reports the Raman spectra of bukovskýite and a similar colloidal mineral phase and relates the spectra to the molecular structure of this sulfoarsenate mineral 20, 21. Infrared spectrum of bukovskýite in the range from 2000 to 600 cm −1 has been published by Novák et al 6 and in part interpreted.…”

Single‐crystal Raman spectroscopy of natural leiteite (ZnAs2O4) and comparison with the synthesised mineral

“…The structure of claudetite, the monoclinic modification of As 2 O 3 , is also comparable to those of meta arsenites; it consists of an infinite zigzag chain of alternating As and O. [7] Although trippkeite CuAs 2 O 4 and the isostructural schafarzikite Fe 2+ Sb 2 O [8,9] both have infinite arsenite or antimonite chains, leiteite is the only known mineral of its kind. In the first two, the cation is found in an octahedral geometry, whereas Zn is in a tetrahedral geometry in leiteite.…”