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 geometry of the deposit consists of the boudinaged main lens, which pinches and swells in thickness along strike and to depth. It is recognised that the previously modelled hangingwall and footwall domains (1A, 2, 3, 4 and 5) are part of the main lens which anastomoses, splits and merges. All zinc and associated lead-silver mineralisation are governed by this geometry. 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 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. The strike length of mineralisation is approximately 2,400 m. Dip varies between 85° and 40° to the west. The true thickness of the majority of the Mineral Resource is between 3 m and 30 m with the thickest zones occurring to the south. The mineralisation is open at depth. The deepest drill intersection of mineralised material is about 1,140 m below the surface.

Mining at Dugald River is planned to be underground with the long-hole open stoping method favoured. Currently the deposit is accessed by two declines.

The orebody access 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) both Longitudinal and Transverse in the South Mine and modified Avoca stoping or Core & Shell stopes with rib pillars in the North Mine. Level intervals occur every 25m and stopes have a strike length of 15m.

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);
- Transverse SLOS, for stopes where the orebody thickness lends itself to sequential stope extraction retreating along cross-cuts;
- 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 for stope types were set as Longitudinal 90%, Modified AVOCA / Core & Shell with rib pillars 75% and Crown stopes 50%-90%.

The underground (UG) mine is accessed via two separate declines and as such the mine is split into two – north and south, although both declines are connected via a link drive approximately every 150m vertically at the base of each production Panel. As at 30 June 2021, 8,621m of decline has been mined, along with a further 63,011m m of lateral development (excluding 2264m of paste development).

Currently, six raise-bored ventilation shafts have connection to the surface:
- The southern Fresh Air Raise (FAR1) – at 3.5 m diameter and 90m depth;
- The southern Fresh Air Raise (FAR2) – at 5.0 m diameter and 190 m depth; with a 120m and 130m extensions to the 340 level and 490 level respectively;
- The southern Return Air Raise (RAR1) – at 5.0 m diameter and 154 m depth; with a 375m extension (multiple holes) to the 565 level;
- The southern Return Air Raise (RAR2) – at 5.0 m diameter and 197 m depth; with a 270m extension (multiple holes) to the 490 level and a further 135m extension to 640 leve;
- The northern Fresh Air Raise (FAR) at 3.5 m diameter and 165 m depth with a 275m extension (multiple holes) to the 490 level and a further 130m extension to the 640 level;
- The northern Return Air Raise (RAR) at 5.0 m diameter and 104 m depth with a 310m extension (multiple holes) to the 490 level and a further 140m extension to the 640 level;
- On each return shaft collar there is an exhaust fan drawing approximately 270-300m3/s.

There is also a secondary RAR system in the north and south mines comprising of LHW and 3.0-3.5m raisebored holes that have connections to each production level where there is access.

Secondary egress is provided by link drives between the South & North declines. These link drives are positioned at the base of each production Panel. The lowest connection to date has been made at the base of Panel 4 on the 640 Level.

An internal ladderway also exists in the South mine between the 50 and 200 Levels. In addition, strategically placed refuge chambers are to be found throughout both mines.

The metallurgy process proposed for the Dugald River deposit involves crushing and grinding.

The metallurgical process for treatment of Dugald River ore involves crushing, grinding followed by sequential carbon/lead/zinc flotation to produce separate lead and zinc concentrates. The carbon concentrate is a waste product and reports to final tailings. This process, and the equipment used, is conventional for this style of mineralisation and used worldwide.

The Dugald River processing facility was commissioned with production commencing in October 2017, with nameplate throughput reached after 7 months of operation(May 2018). Both lead and zinc concentrate produced at Dugald River meet saleable grade and impurity specifications.

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.