Mineralogy and Weathering of Realgar-Rich Tailings At a Former As-Sb-Cr Mine At Lojane, North Macedonia

Abstract

In the Lojane area (North Macedonia) ores of Sb (stibnite), As (realgar), and Cr (chromite) were mined and processed in a metallurgical plant until 1979. Over one million tons of flotation tailings containing As, Sb, and other hazardous substances are located in an open dump site for flotation waste created by the mine. The tailings site is completely unprotected, and its orange color reflects a very high concentration of arsenic (fine-grained realgar superficially altered to pararealgar). In order to better understand the weathering behavior of these tailings, which is necessary to evaluate the environmental risks (mainly from the mobilization of As-Sb-Cr), solid waste material was sampled and studied from the chemical and mineralogical point of view. The material was characterized by inductively coupled plasma-mass spectrometry (ICP-MS), inductively coupled plasmaoptical emission spectrometry (ICP-OES), X-ray diffraction analysis (both single crystal and powder), scanning electron microscopy (SEM) with energy-dispersive microanalysis (EDX), Raman spectroscopy, and transmission electron microscopy (TEM) with selected area electron diffraction (SAED), energy-dispersive X-ray analysis (EDX), and electron energy loss spectrometry (EELS). The studied tailings material is comprised mostly of well-crystallized realgar, gypsum, and quartz, and minor amounts of stibnite, pararealgar, chromite, and sulfur. Very minor pyrite is found within quartz aggregates. The most abundant secondary phase, which forms thin coatings around realgar and stibnite grains, is an As-Sb-Fe-Ca-(Ni)-oxide/ hydroxide in which the As:Sb ratio varies from ca. 2:1 to 1:2.2 and Fe contents are variable.

Processes of metastable-mineral formation in oxidation zones and mine waste

“…The transient X-ray amorphous materials are related to the antimony-bearing phases with pyrochlore structure, such as oxycalcioroméite (Ca 2 Sb 2 O 6 O) or bindheimite (Pb 2 Sb 2 O 6 O). Similar materials were also reported recently by Đorđević et al (2019) from weathering of realgar-rich tailings which are rich in Sb but depleted in Fe. Our on-going studies indicate the presence of similar materials during weathering of Hg-tetrahedrite.…”

Application of a handheld Raman spectrometer for the screening of colored secondary sulfates in abandoned mining areas—The case of the São Domingos Mine (Iberian Pyrite Belt)

“…Ideally, these techniques should allow on‐site measurements for avoiding any transformations of investigated samples during sampling and storing. Raman spectroscopy has established as a powerful nondestructive tool for rapid and reliable discrimination of various metal‐bearing sulfates that occur at sites featuring sulfide‐weathering processes, but typically as the laboratory‐based method 9–13 . The recent progress in miniaturization has led to the development of portable and, particularly, handheld Raman instruments that are easy to operate and are capable of obtaining Raman spectra in the field.…”

“…Raman spectroscopy has established as a powerful nondestructive tool for rapid and reliable discrimination of various metalbearing sulfates that occur at sites featuring sulfideweathering processes, but typically as the laboratory-based method. [9][10][11][12][13] The recent progress in miniaturization has led to the development of portable and, particularly, handheld Raman instruments that are easy to operate and are capable of obtaining Raman spectra in the field. Although such instruments are widely available, especially spectrometers of the handheld size are still not routinely used in mineralogical and geological research and only several studies included them as a technique for the in situ detection of sulfates, arsenates, and other minerals.…”

Multivariate Statistical Methods in Determining the Spatial Distribution of Chemical Elements in Soils (Kumanovo Region, North Macedonia)

“…It is important to mention that the source of pollution with PTEs is also the closed As-Sb-Cr mine "Lojane" and metallurgical plant in the northwestern part of the study area. This assumption is supported by high arsenic concentrations in soil and ground water detected in the vicinity of flotation tailings landfill (UNDP, 2007;Alderton et al 2014;Đorđević et al, 2019;Stafilov et al, 2022b). The geological map of the study area is shown in Figure 2.…”