The historic mine waste site at Nöckelberg, Austria – exploration and re-use potential

For its thermo-electric properties, the mineral tennantite is a much sought-after commodity which occurs in historic mine waste heaps. The mining site Nöckelberg, located near Leogang in the province of Salzburg, offers such a waste heap. Here, copper, nickel and cobalt mining took place in the 19^th and early 20^th century. Dominant ore minerals include tennantite, chalcopyrite, cinnabar, galena and bornite, embedded in a matrix of magnesite, dolomite and quartz. The waste heap consist of pebble- to boulder-sized rock fragments which still contain visible quantities of tennantite.

To define the geometry of the waste heap, quantify its volume and characterize the ore content, a multi-disciplinary study was carried out. Terrain modelling aimed at reconstructing the ground surface prior to mining. Geochemical analyses comprised whole rock XRF to quantify element concentrations, XRD to describe bulk mineralogy, and SEM to study mineral composition.

3D modelling reveals a mean waste pile thickness of 4.2 m and a volume of 26,000 m³. The material contains 4% copper iron sulfides (bornite, chalcopyrite and tennantite) and As and Cu elemental concentration of 2% and 3% respectively. The 100 µm-sized tennantite grains are intertwined with chalcopyrite and show a typical composition of 37 at.% Cu, 10 at.% As, 3 at.% Sb, 7 at.% Fe and 43 at.% S.

These results indicate a (small) tennantite resource potential sourced from mine waste material. Separation and beneficiation tests are currently ongoing.

The START project is co-funded by the European Union. Views and opinions expressed are those of the authors.