The geology of Wetar Island is composed entirely of Neogene volcanic rocks and minor oceanic sediments. Submarine basaltic-andesites with local pillows form the volcanic basement to the island. The basaltic-andesites are intruded by rhyo-dacite domes and overlain by dacitic lavas, tuffs and breccias, debris flows, globerigina limestones and lahar deposits. The age of the mineralisation has been estimated at around 4.7 million years.

Copper mineralisation at both Kali Kuning and Lerokis occurs predominantly within coherent massive sulphide units with a lesser amount of generally lower grade material occurring within intensely clay-sericite pyrite altered andesitic tuffs in the footwall and lateral extent of the massive sulphide units. Based on Finders’ drilling, the Kali Kuning massive sulphide resource has been re-classified into three metallurgical sub-types – Leached, Transition zone and Primary massive sulphide. The Leached and Transition types reflect incipient in-situ leaching of the massive sulphide unit by natural groundwater. The Transition zone material although of lower copper grade than the main Primary massive sulphide (1.5% vs 2.9%) contains a higher proportion of readily leachable copper minerals.

Ore and waste mining continued at Kali Kuning during the year, with the focus of mining in the northern end of the open pit to bring the floor level with the southern end of the pit. By year end, the majority of the exposed open pit floor was ore, with high grade, black massive sulphide predominating. This was also reflected in a progressive increase in the grade of ore stacked as mining progressed through lower grade transitional ore into the higher grade massive sulphide ore that comprises most of the orebody at Kali Kuning.

Finders has operated a sulphide heap leach and solvent extraction-electrowinning (SX-EW) copper cathode demonstration plant on Wetar Island since 2009. In 2014, the SX-EW plant was upgraded to 3,000tpa which validated the economics for the expansion of the Project to a capacity of 28,000tpa. A new 25,000tpa SX-EW plant was commissioned in May 2016 with first copper plated and stripped in June 2016. By late 2016, the new SX-EW plant was operating at about nameplate capacity.