Great Southern Copper Reports 'Excellent' Copper, Silver Recoveries at Mostaza Deposit in Chile

05:34 AM EDT, 09/21/2026 (MT Newswires) -- Great Southern Copper (GSCU.L) confirmed "excellent" metallurgical recovery and concentrate results from the Mostaza deposit at the Cerro Negro prospect of its Especularita project in Chile. Preliminary metallurgical test-work on high-grade samples from the deposit registered recoveries of over 90% for copper and 85% for silver, with final concentrate grades averaging 27% copper and 1,414 grams per ton of silver, according to a Monday filing. The copper-gold-silver exploration company, which holds rights to own 100% of the Cerro Negro prospect, plans to start the phase 4 drilling program at the site in October.