Capricorn Copper consists of several structurally controlled, sediment-hosted copper deposits located within the Western Fold Belt of the Mt Isa Inlier.

The structures are Middle Proterozoic in age, and the region hosts significant known deposits, including Mount Isa (Cu, Pb, Zn, Ag), Century (Zn, Pb, Ag), Cannington (Ag, Pb, Zn), and Osborne & Ernest Henry (Cu, Au).

There are two dominant styles of mineralisation at Capricorn Copper:
- breccia-hosted within quartzites – Mammoth and Greenstone deposits; and
- shear-hosted within shales/siltstones – Esperanza, Esperanza South and Pluto deposits.

Mammoth
Mineralisation occurs in multiple lenses as 10–30m wide breccia zones developed at the point of intersection between major structures.

Mineralisation consists of breccia-fill bornite, chalcopyrite, chalcocite, pyrite, and locally arsenopyrite, with a gangue of chlorite-haematite. Chalcocite is present closer to surface with chalcopyrite and bornite dominant at depth.

Greenstone
Mineralisation occurs in multiple lenses and comprises veinlets and breccia-fill bornite, chalcopyrite, chalcocite and pyrite, with a gangue of chlorite-haematite.

Chalcocite is present closer to surface with chalcopyrite and bornite dominant at depth.

Esperanza, Esperanza South and Pluto
Mineralisation occurs as shear-hosted mineralisation in shale/siltstone, with chalcocite veins and bornite within the upper levels, transitioning to chalcopyrite-pyrite mineralisation at depth.

Copper species include chalcocite, covellite, bornite, chalcopyrite and native copper, and post- date and replace pyrite.

Esperanza – mineralisation is hosted in graphitic siltstones and consists of a supergene chalcocite blanket with lesser native copper underlying a silicified cap, with mineralisation grading into chalcopyrite at depth. Most of the chalcocite blanket was mined by previous open pit mining operations.

Esperanza South – mineralisation occurs over a 50–75m wide zone in variably silicified siltstones, locally brecciated and plunging steeply south, sub-parallel to the Esperanza fault Higher grade copper mineralisation occurs in a westerly hanging-wall zone and an easterly footwall zone, with stockwork mineralisation between these two zones. Veins and disseminations of chalcopyrite occur with bornite and pyrite, with grades typically 2–3% Cu, but supergene chalcocite has been shown to increase grades to 4% Cu and above.

Pluto – the Pluto deposit is highly leached in a zone approximately 200m in strike and 2–30m in width, and contains predominantly supergene chalcocite, cuprite and native copper and is therefore metallurgically distinct compared with the other deposits.

Mineralisation is predominantly copper accompanied by silver. Silver grades have tended to increase with depth at Esperanza and Esperanza South. Minor cobalt, nickel and arsenic mineralisation is also present, typically associated with pyrite, with higher arsenic mineralisation within some Mammoth lodes.

Of the five known deposits at Capricorn Copper with three currently in production:

- Esperanza South (‘ESS’), Mammoth and Greenstone. The other two deposits – Esperanza and Pluto – are currently planned to come into production from 2026.

Access to ESS and Mammoth is via two separate declines. Access to Greenstone is via an access drive from the Mammoth decline.

At Mammoth, the historical decline has been rehabilitated and extended to provide access to mining areas known as Mammoth Remnants and Mammoth Deeps, and a further access drive from the Mammoth decline is planned to access Esperanza and Pluto for mining in the future.

At ESS, Capricorn Copper has developed new mine infrastructure comprising the decline, ventilation rises, power supply network and groundwater pumping.

At Greenstone, a separate return air rise and emergency egress rise have been developed.

Mining in ESS applies sub-level caving. Mining at Mammoth and Greenstone applies long-hole open stoping with waste-rock or paste fill.

In the future, mining of Esperanza and Pluto will employ LHOS mining methods.

Ore is transported by truck to surface via the ESS and Mammoth declines (as applicable).

At Greenstone and Mammoth waste rock is partially used as backfill with surplus waste rock trucked to surface and deposited in the waste rock dump.

The Capricorn Copper operations team is responsible for operational management of the mine, including short-to-long term planning, mine design and scheduling, ventilation, drill and blast design, mine survey, geotechnical, mine control and backfill.

Mining is performed by a mining contractor. The mining contractor is responsible for underground mining and maintenance activities, with other specialised contracts for drilling consumables, explosives and ground support.

Crushing:
- Ore mined is hauled to the surface via truck to the ROM surface stockpile;
- Ore is then fed via front-end loader to a single toggle jaw crusher;
- Crushed ore is then fed to the crushed ore stockpile (‘COS’) via conveyor.

Grinding:
- Ore is reclaimed from the COS by plate feeders and delivered to the grinding circuit via conveyor;
- The grinding circuit has two stages comprising a SAG mill and secondary ball mill;
- Target grind size of approximately 106 µm (micrometre) particles;
- The ball mill operates in a closed circuit with hydrocyclones. Oversize material to the ball mill for further grinding and undersize material is the feed for the flotation circuit.

A critical component of the Capricorn Copper refurbishment and restart project was the refurbishment of the Capricorn Copper process plant following an extended period in care and maintenance (2013– 2016).

The Capricorn Copper processing plant is a conventional flow sheet involving crushing, grinding, screening and flotation to produce mineral concentrates.

Screening:
- SAG mill discharge is screened via trommel, with oversize material recycled back to the SAG mill for further grinding via a series of scats conveyors. Undersize material is passed to a cyclone feed sump and from there to the ball mill.

Flotation
- The first stage of flotation is a single train of 4 x 100m3 flotation tank cells where Lime, collector and frother are added;
- The first rougher cell produces final mineral concentrate grade material that is fed to the concentrate thickener;
- Concentrate from the remaining three rougher cells is reground in a high-intensit ........