Pickeringite from the Stone Town Nature Reserve in Ciężkowice (the Outer Carpathians, Poland)

Abstract

Pickeringite, ideally MgAl2(SO4)4·22H2O, is a member of the halotrichite group minerals XAl2(SO4)4·22H2O that form extensive solid solutions along the joints of the X = Fe-Mg-Mn-Zn. The few comprehensive reports on natural halotrichites indicate their genesis to be mainly the low-pH oxidation of pyrite or other sulfides in the Al-rich environments of weathering rock-forming aluminosilicates. Pickeringite discussed here occurs within the efflorescences on sandstones from the Stone Town Nature Reserve in Ciężkowice (the Polish Outer Carpathians), being most probably the first find on such rocks in Poland. This paper presents mineralogical and geochemical characteristics of the pickeringite (based on SEM-EDS, XRPD, EPMA and RS methods) and suggests its possible origin. It belongs to the pickeringite–apjohnite (Mg-Mn joints) series and has the calculated formula Mg0.75Mn0.21Zn0.02Cu0.01Al2.02(S0.99 to 1.00O4)4·22H2O (based on 16O and 22H2O). The unit cell parameters refined for the monoclinic system space group P21/c are: a = 6.1981(28) Å, b= 24.2963(117) Å, c = 21.2517(184) Å and β = 100.304(65)°. The Raman spectra (SO4) bands are the intensive 994 cm−1 and a low-intensive 975 cm−1 (ν1), low-intensive 1081, 1123 and 1145 cm−1 (ν3), 524, 467 and 425cm−1 (ν2), 615 cm−1 (ν4), while those at 344 and 310 cm−1 are attributed to νg H2O and at 223 cm−1 to the lattice modes. Crystallization of pickeringite within the particular tor resulted from a certain set of conditions: climatic (e.g., season, temperature, humidity), physicochemical (e.g., pH, concentration), mineral (the presence of pyrite), and site-related (location and efflorescence protection). The sulfate ions could have been derived from oxidation of pyrite in the Ciężkowice sandstones and possibly are related to local mineral waters.

Orange Pickeringite from the Algares 30-Level Adit, Aljustrel Mine, Iberian Pyrite Belt, Portugal

“…The ternary diagram plotted in Figure 8 shows that they are both pickeringite. Collected SEM images illustrate the aggregates of fine-acicular crystals (Figure 9), showing the typical morphology of these minerals in accordance with published papers (e.g., [22,26,[36][37][38]). The approximate chemical formula was also calculated through EDSquantification (Tables 4 and 5), following the same methodology used before, based on Collected SEM images illustrate the aggregates of fine-acicular crystals (Figure 9), showing the typical morphology of these minerals in accordance with published papers (e.g., [22,26,[36][37][38]).…”

“…Collected SEM images illustrate the aggregates of fine-acicular crystals (Figure 9), showing the typical morphology of these minerals in accordance with published papers (e.g., [22,26,[36][37][38]). The approximate chemical formula was also calculated through EDSquantification (Tables 4 and 5), following the same methodology used before, based on Collected SEM images illustrate the aggregates of fine-acicular crystals (Figure 9), showing the typical morphology of these minerals in accordance with published papers (e.g., [22,26,[36][37][38]). The approximate chemical formula was also calculated through EDSquantification (Tables 4 and 5), following the same methodology used before, based on four sulphur atoms, maintaining the ratio A:B ∼ = 1:2.…”

Raman spectroscopy of anhydrous and hydrated aluminum sulfates: Experience from burning coal heaps

“…Furthermore, natural and synthetic specimens may have significantly different spectral features, as reported in literature. [44,64,65] However, the Raman spectrum of pickeringite observed within this work agrees with the spectrum of pickeringite reported by Locke et al [46] and Marszałek et al [68] : Two intense bands at approximately 995 and 975 cm À1 provide reliable evidence.…”

The role of efflorescent salts associated with sulfide-rich mine wastes in the short-term cycling of arsenic: Insights from XRD, XAS, and µ-XRF studies

“…generally crystallize in open areas exposed to intense evaporation in arid climates (Marszałek et al, 2020). Minerals of the halotrichite group such as apjohnite (Mn 2+ Al 2 (SO 4 ) 4 •22H 2 O) and halotrichite (Fe 2+ Al 2 (SO 4 ) 4 •22H 2 O), are more stable and J o u r n a l P r e -p r o o f precipitate later than the simple magnesium such as epsomite (e.g.…”