Bioleaching, mediated by selected microflora, offers a more environmentally friendly and cost-effective alternative to traditional mining techniques by transforming metals from sulfide ores into water-soluble forms. Pyrite ores often contain valuable rare or noble metals, such as gold (Au), silver (Ag), nickel (Ni), and cobalt (Co), which can be leached through the metabolic activity of specific chemoautotrophic microorganisms. This study investigates the adaptation process of the Acidithiobacillus ferriphilus bacterial strain, originally isolated from acid mine drainage (AMD), for the bioleaching of pyrite. The progress of the bioleaching process was evidenced by the release of iron (3.6 mg/mL) and significant quantities of gold (0.21 mg/L, equivalent to 3 g/t) into the post-culture liquid. The results indicate that the most effective bioleaching was achieved during the final adaptation stage, utilizing a medium with 7% pyrite content and a 0.75% supplement of an easily accessible energy source in the form of iron sulfate. These findings confirm the potential of the A. ferriphilus strain for pyrite bioleaching.

This study evaluates the potential of fine-grained waste gneiss as a soil improver, with particular emphasis on its chemical and grain composition and its effects on plant growth. The experimental material consisted of mixtures of fine-grained waste gneiss with varying proportions (from 0.38% to 7.5% in the pot) supplemented with varying proportions of dolomite (from 0.14% to 0.22% in the pot). Pot experiments were conducted for 57 days under controlled conditions using selected crops. Plant response was assessed based on growth rate, green mass production, and dry mass. For most tested variants, the results demonstrated a dose-dependent enhancement in plant productivity associated with gneiss supplementation. Compared to the control, experiments containing higher proportions of fine-grained gneiss resulted in an increase in green and dry mass from 8.14% to 78.73% and by 12.5% to 96.88%, respectively. Additionally, strong positive correlations between gneiss content and yield parameters (Pearson’s r > 0.8) were observed. In contrast, the dolomite fraction mainly conceptually affected soil chemical properties, including calcium and magnesium availability and pH stabilization. Overall, the findings suggest that fine-grained waste gneiss acts as a growth-promoting soil conditioner, as evidenced by the marked improvement in plant biomass. The findings confirm the high potential of waste gneiss as a functional soil improver, supporting sustainable resource management and aligning with the principles of the circular economy.

Study of detrital gold grains from modern sediments in the bed of the Wierzbiak River in Lower Silesia (SW Poland) provided insights into their morphological and chemical characteristics. The gold grains exhibit low shape diversity and a high degree of edge rounding. Chemically, the gold grains are homogeneous, consisting of native gold with a maximum silver content of up to 20 wt.%. The grains analysed also contain micro-inclusions, mainly composed of Ni-Co-Fe sulpharsenides and sulphides, such as pyrite, chalcopyrite, galena and native bismuth, pointing to an association of mesothermal Fe-Ni-Co-Bi-As mineralization type. The mineral inclusions observed are not typical for the quartz veins of the Wądroże Wielkie Massif but resemble the mineralization present in the polymetallic veins of the Kaczawa Metamorphic Complex. The results of this study support a thesis of a complex genesis of the local Lower Silesian gold-bearing Cenozoic placers, involving both the weathering of local quartz veins of the Wądroże Wielkie Massif and potential contributions from other ore sources in the region. Further geophysical and borehole studies are needed to more accurately assess the gold resources in the Fore-Sudetic Block, especially in the watersheds of the Wierzbiak and Nysa Szalona rivers.