Historic mine waste - A potential source for critical metals and environmental contamination? A case study from Styria, Austria

The European Union has set a target of producing 10 % of its Critical Raw Materials (CRMs) demand by 2030, in order to reduce its dependency on imports (Critical Raw Materials Act, 2024). Achieving this short-term goal is only possible through an increased CRM supply from non-traditional sources, such as historic mine wastes (HMWs). As early mining prioritized high-grade ore and relied on less effective separation techniques, HMWs can still have elevated concentrations of critical and precious metals. Sulfide-rich waste is of particular interest, as it can contain a variety of elements that tend to associate with sulfide minerals (including Ag, As, Au, Cu, Co, Ni, Sb and Te) and can also cause environmental impacts, such as acid mine drainage or metal(loid) contamination of soil and water (Göbel, 2024; Hiller, 2024; Gopon et al., 2025).

To evaluate the residual CRM potential and the associated environmental impacts of HMWs, detailed sampling campaigns have been carried out in a former copper-gold mining district in the Upper Mur Valley (Styria, Austria). In this area, sulfide-rich ore was primarily mined during the 18^th and 19^th century, resulting in numerous small, generally overgrown waste rock piles. Whole rock geochemical analyses of the sampled waste rock show a strong heterogeneity of the CRMs present in the HMWs, indicating spatial differences in the mined ore. Elevated concentrations of copper, arsenic (both up to 0.6 wt.%), and gold (up to 2.4 g/t) highlight a remaining economic potential for the recovery of both critical and precious metals.

Additionally, a significant environmental impact was revealed by a monthly stream water sampling campaign in combination with metal(loid) analysis by inductively coupled plasma mass spectrometry (ICP-MS). In several streams at the study site, the concentration of arsenic surpasses the WHO drinking water guideline of 10 µg/l (WHO and UNICEF, 2018), with maximum concentrations reaching more than 500 µg/l. The identified sources for the release of arsenic are weathering HMWs and effluent water from open mine adits. Strong spatial heterogeneities of the arsenic concentration and speciation in the stream waters also indicate variations in the waste material and favourable conditions for the release of arsenic.

The results of waste rock and stream water analyses highlight the importance of an interdisciplinary approach on HMWs, which can be both of economic interest and environmental concern at the same time. The work at the study site in the Upper Mur Valley is part of the SCIMIN-CRM project, which is evaluating the CRM potential of mine wastes at four different locations across Europe and is funded by the European Union (Horizon Europe, No. 101177746).

 

References:

Göbel, E., 2024, Sulfide Geochemistry of the Hohen Tauern Historic Gold Districts (Austria). Montanuniversität Leoben.

Gopon, P., et al., 2025, Revealing Yukon’s hidden treasure (…). Mineralium Deposita, doi:10.1007/s00126-024-01325-9.

Hiller, J., 2024, A green future from a contentious past: Gold and critical metals in a historic arsenic mining district Straßegg (Styria). Montanuniversität Leoben.

WHO and UNICEF, 2018, Arsenic Primer: Guidance on the Investigation & Mitigation of Arsenic Contamination. ISBN: 978-92-806-4980-2.