The Dugald River style of mineralisation is a sedimentary and shear hosted base metal deposit. The main sulphides are sphalerite, pyrite, pyrrhotite and galena with minor arsenopyrite, chalcopyrite, tetrahedrite, pyrargyrite, marcasite and alabandite.

The deposit is located within a 3km-4km along strike north-south trending high strain domain named the Mount Roseby Corridor and is hosted by steeply dipping mid Proterozoic sediments of the Mary Kathleen Zone in the Eastern Succession of the Mount Isa Inlier. The host sequence is composed of the Knapdale Quartzite and the Mount Roseby Schist Group (which includes the Hangingwall calc-silicate unit, the Dugald River Slate and the Lady Clayre Dolomite). The sequence is an interbedded package of greenschist to amphibolite grade metamorphosed carbonate and siliclastic lithologies.

The main Dugald River lode is hosted within a major N-S striking steeply west dipping shear zone which cross cuts the strike of the Dugald River Slate stratigraphy at a low angle. All significant zinc-lead-silver mineralisation is restricted to the main lode. Lesser-mineralised hanging wall and footwall lenses are present. Three main mineralisation textures/types are recognised, including banded, slatey breccia, and massive breccia.

The mineralogy of the Dugald River lode is typical of a shale-hosted base metal deposit. The gangue within the lode is composed of quartz, muscovite, carbonates, K-Feldspar, clays, graphite, carbonaceous matter and minor amounts of calcite, albite, chlorite, rutile, barite, garnet, and fluorite.

The mineralised zone extends approximately 2.4km in strike length and up to 1.4km down-dip.

The orebody is split into a north and south mine, due to its 2 km strike length and a low-grade zone at the extremities of the orebody.

The north mine is narrow (average ~5 m true width) and sub-vertical. The south mine is wider than the north mine with a flexural zone in the centre. The south mine is narrow and steep in the upper zone (~top 200 m from surface) and lower zone (~below 700 m from surface). The central zone is flatter and thicker than the upper and lower zones.

Mining methods for the mine are Sub-Level Open Stopes (SLOS) in the South Mine and modified Avoca stoping or Core & Shell stopes with rib pillars in the North Mine with a 25m level interval and variable stope strike length of 15 m to 30m.

The stopes are broken into the following categories:
- Longitudinal SLOS, for stopes upto 10-15m wide horizontally. (Where the orebody has thickened adjacent stopes are mined in sequence after paste filling).
- Crown pillar SLOS, for the top level of each panel where stoping occurs directly below a previously mined area.
- Modified Avoca stopes/Core & Shell Stopes for the North Mine.

Fill Dilution and Stope Recovery Factors:
- Floor 0.15 m, Backs 0.5 m and Wall fill ranges from 1 m to 1.5 m dilution.
- Recoveries Longitudinal 95%, Modified AVOCA / Core & Shell with rib pillars 75% and Crown stopes 90%.

The underground (UG) mine is accessed via two separate declines. The mine is split into two – north and south, though both declines are connected via a link drive approximately every 150m vertically -the base of each production Panel. As at 30 June 2019, 7,577m of decline is in place, along with a further 45,810 m of lateral development.

The metallurgy process proposed for the Dugald River deposit involves crushing and grinding followed by floatation and filtration to produce separate zinc and lead concentrates for sale.

Deleterious elements include manganese and carbon, which have been estimated in the block model. Manganese percentage in the zinc concentrate is calculated as a postprocessing
step to allow the generation of a value that can be used for the Ore Reserves.