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.

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 the Ridgeway 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.