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).

Concentrator 1: • Primary crushing in a 60-inch x 113-inch gyratory crusher. This was the main primary crusher for the original Cadia concentrator and now primarily used for surface stockpile reclaim; • Coarse ore stockpile (COS) to a live capacity of 40,000 t and subsequent reclaim facilities; • Distribution bin and double-deck vibrating screens for feed size preparation; • Secondary crushing, treating screen oversize, using MP1000 cone crushers; • High pressure grinding rolls (HPGR) unit treating screen undersize prior to the SAG mill; • Primary open circuit milling in a single 40-ft SAG mill fitted with a 20 MW motor. The motor will be upgraded to 22 MW. Oversize pebbles from the SAG mill are returned to the distribution bin; • Secondary milling in three ball mills, with the two original mills fitted with 8.7 MW motors, and a more recently installed third ball mill with a 16 MW motor. The mills are in closed circuit with cyclone classification for a target grind size of P80 of 150–190 µm. Concentrator 2: • Reclaim and conveying system to transfer ore from Concentrator 1 COS to Concentrator 2 facilities; • Secondary and tertiary crushing using MP800 cone crushers and open circuit prescreening; • Dedicated coarse (crushed) ore stockpile (COS) and apron feeder reclaim facilities; • Primary open circuit milling in a single SAG mill fitted with a 7.5 MW motor; • Secondary milling using a 7.5 MW ball mill and parallel Vertimill VTM1250, in closed circuit with classifying cyclones. • Tertiary milling using a Vertimill VTM 3000. Cadia’s operating and financial performance in FY22 was impacted by reduced throughput rates during the planned replacement and upgrade of the SAG mill motor which commenced in early July 2021 and was successfully completed in November 2021, together with the expected decline in grade.

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