The Cadia East deposit occupies a mineralized zone 2.5 km in strike length, 600 m in width and over 1,900 m in vertical extent. It is located below and to the east of the Cadia Hill orebody.

Mineralization is spatially and temporally associated with a swarm of narrow Early Silurian, alkalic monzonite and monzodiorite dykes that intrude the Ordovician Forest Reefs Volcanics, a thick succession of volcanic (lavas and sub-volcanic intrusions) and associated clastic rocks (debris flow volcaniclastics, sandstones, siltstones and minor limestones).

The Cadia East mineralization consists of a package of steeply dipping, sheeted quartz veins forming a near vertical slab with dimensions approximately 2.5 km long, greater than 1.6 km deep and at least 200 m to 300 m wide. A high grade gold core is found at depth towards the eastern end of this vein package. Smaller pods of higher grade material are located above and lateral to the high-grade core.

The Cadia Hill deposit is a sheeted quartz vein system located almost entirely within the quartz monzonite porphyry phase of the Cadia Intrusive Suite.

The predominant alteration is propylitic (chlorite-epidote) with narrow domains of structurally-controlled phyllic (sericitic) alteration. Mineralization is in part related to chlorite matrix hydrothermal breccias that cut the deposit.

The vein system forms a broad, 300 m wide tabular envelope that dips 60° to the southwest. Chalcopyrite with lesser bornite, pyrite and gold occur in the quartz veins and as disseminations throughout the intrusive wallrock.

The Ridgeway deposit is a higher grade Au-rich alkalic porphyry deposit. Copper-gold bearing quartz veins are centered on small (50-100 m diameter) multiphase monzonitic ‘pencil’ porphyries and hosted in an Ordovician volcano sedimentary succession. The known vertical extent of the mineralized system is 1,100 m, with the top of the ore zone located 500 m below the present day surface. The deposit remains open at depth.

Mineralization at Ridgeway and Ridgeway Deeps occurs in dense quartz vein stockworks and sheeted arrays localized in and around a small (50 m to 100 m diameter) composite diorite to quartz-monzonite intrusive complex. The most strongly developed quartz stockwork veining and alteration, and the highest copper and gold grades, occur immediately adjacent to the monzonite.

Cadia East deposit is a large underground mining operation using the panel caving method (Cadia East Project). The deposit is mined in a number of lifts each comprising multiple panels.

A feasibility study on mining the Cadia Hill deposit was completed in 1996 with project funding approved in September that year. The feasibility study open pit design, which included a number of planned cutbacks.

Underground mining of the Ridgeway deposit commenced in 2002, with ore being supplied to the new 4 Mtpa Ridgeway concentrator adjacent to the Cadia concentrator. The upper portion of theRidgeway deposit has been mined using sub-level caving (SLC).

The process plant comprises a crushing, grinding and flotation circuit to produce a gold rich copper concentrate. A gravity circuit recovers a proportion of the gold which is smelted on site to produce gold doré. A notable aspect of Concentrator One’s design is the use of high capacity equipment in a single processing line to minimise capital and operating costs.

Underground ore from Ridgeway is processed in Concentrator Two, which uses similar processes to the adjacent Concentrator One, with the major difference being the size of the facility, which is designed to treat lower volumes of higher grade ore.

The concentrates from both treatment plants are combined and pumped as slurry to a filtration plant where the concentrate is de-watered and transported by rail to Port Kembla for export.