Copper Deportment in a VMS-Hosted Ore from Wetar via Diagnostic Sequential Leaching

Copper (Cu) is predominantly sourced from chalcopyrite (CuFeS), which accounts for about 70% of the world's copper reserves.However, chalcopyrite is notoriously refractory to leaching under standard acidic conditions, leading to slow dissolution kinetics and low extraction efficiency.This study investigates the copper deportment in a volcanogenic massive sulfide (VMS)-hosted ore from Wetar Island, Maluku, Indonesia, by employing diagnostic sequential leaching (DSL).The DSL method sequentially leaches the ore with specific reagents to dissolve different copper-bearing mineral fractions.The Wetar ore sample (~2% Cu) was subjected to a water wash, dilute sulfuric acid leach, and a sodium cyanide leach, sequentially, followed by analysis of the residual solid.Results show that only ~2% of the total copper was water-soluble, ~10% was acid-soluble (as oxides/carbonates), and ~43% was extracted by cyanide (as secondary Cu-sulfides).The largest fraction, ~45%, was left as residual copper.This indicates that while more than half of the copper in this ore exists in easily leachable secondary sulfides and oxides, nearly half remains as refractory primary sulfide (chalcopyrite).These findings inform the design of an optimal extraction strategy, suggesting that conventional leaching could recover a majority of the copper; however, additional measures (e.g., oxidants) would be required to liberate the remaining chalcopyrite-hosted copper.