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Alunogen from the sulfate efflorescence of the Stone Town Nature Reserve in Ciężkowice (the Outer Carpathian Mountains, Poland)

Marszałek Mariola, Gaweł Adam

Geology, Geophysics and Environment

2023

Vol. 49, no. 2

139--156

Alunogen (Al2(SO4)3∙17H2O), a rare secondary mineral, has been found in the efflorescence on sandstones from the Stone Town Nature Reserve in Ciężkowice, southeastern Poland. This is probably the first find of this salt on such rocks in Poland. Alunogen forms in various geological environments, but mainly from the oxidation of pyrite and other metal sulfides in ore deposits and Al-rich Earth materials under low-pH conditions. Its crystallization at this particular site depends on a set of necessary physicochemical (pH, concentration), climatic (season, temperature, humidity), site-related (location and protection of efflorescence), and mineralogical (the presence of pyrite) conditions. This paper presents the mineralogical and geochemical characteristics of the alunogen from the Stone Town Nature Reserve (based on SEM-EDS, XRPD, EPMA and Raman spectroscopy methods) as well as of the efflorescence itself (based on XRPD and STA coupled with QMS and FTIR for the analysis of gas products). Crystals of alunogen take the shape of flakes, often with a hexagonal outline, clustered in aggregates forming a cellular network. Its calculated formula is (Al1.96Fe3+ 0.01)∑1.97(SO4)3∙17H2O (based on 12 O and 17 H2O). The unit-cell parameters refined for the triclinic space group P1 are: a = 7.423 (1) Å, b = 26.913 (5) Å, c = 6.056 (1) Å, α = 89.974 (23)°, β = 97.560 (25)°, γ = 91.910 (22)°. The Raman spectra (SO4) bands are: intensive 995 cm−1 (ν1); low-intensive 1069, 1093 and 1127 cm−1 (ν3); low-intensive 419 and 443; medium-intensive 470 cm−1 (ν2); and medium-intensive 616 cm−1 (ν4). Those at 530, 312 and at 338 cm−1 are assigned to water vibrations and those at 135, 156, 180 cm−1 to the lattice modes. Although the efflorescence contained an admixture of other minerals (pickeringite, gypsum and quartz), the predominant alunogen is almost chemically pure and the above parameters are consistent with the values reported in the literature for alunogen from different locations and of various origins.

Mineralogical and geochemical studies of secondary mineral assemblages related to deterioration of building materials

Marszałek Mariola, Dudek Krzysztof, Gaweł Adam, Czerny Jerzy

Geological Quarterly

2019

Vol. 63, No. 4

683--698

The study was aimed at mineralogical and geochemical characteristics of secondary phases related to deterioration of historic building materials. The investigations, carried out in the Holy Trinity Basilica in Kraków, Poland, focused on the southern facade of the 17th-century Myszkowskis Chapel, built of the Miocene Pińczów limestone. Lower part of the facade is covered with a cement render, and the exposed foundations are made of Jurassic limestone and Cretaceous sandstone, both of local origin from the Kraków region and neighbouring Carpathians, in the form of irregular blocks bound with a cement mortar. The wall surface exhibits clear signs of damage; from dark grey soiling and scaling to efflorescences. Sampled materials, deteriorated, altered crusts and efflorescences were analysed with optical and scanning electron microscopy, X-ray diffraction, and Raman microspectroscopy methods. The secondary minerals distinguished include abundant gypsum CaSO42H2O, less common thenardite Na2SO4 (and/or mirabilite Na2SO410H2O), aphthitalite (K, Na)3Na(SO4)2, darapskite Na3(SO4)(NO3)H2O, ettringite Ca6Al2(SO4)3(OH)12 26H2O, monosulphite Ca4Al2O6SO311H2O, as well as scarce nitre KNO3, nitratine NaNO3 and halite NaCl. Gypsum usually forms surface crusts and fills the pores inside some materials. The efflorescences, sampled from the exposed foundations, consisted of thenardite and/or mirabilite, aphthitalite and darapskite, whereas ettringite and monosulphite were connected with cement renders. Traces of nitre, nitratine and halite were detected at various elements of the chapel facade and foundations. The origin of the salts is related to composition and physicochemical properties of the building materials, as well as to anthropogenic factors.