Wetar Island is composed of Neogene volcanic rocks and minor oceanic sediments and forms part of the Inner Banda Arc. The island preserves ~4.7 million-year-old precious metal-rich volcanogenic massive sulphide and barite deposits.

The polymetallic massive sulphides are dominated by pyrite, with minor primary chalcopyrite and lesser bornite cut by late fractures infilled with sulphosalts, tennantite-tetrahedrite and enargite. The sulphosalts have replaced primary chalcopyrite and bornite to varying extents across Kali Kuning, Lerokis and Partolang, and these have in turn been replaced by supergene chalcocite and covellite to varying extents.

Barite-rich orebodies are developed on the flanks of the sulphide units and locally overly the massive sulphides.

Sulphide mounds showing talus textures are localised onto faults, which provided the main pathways for high-temperature hydrothermal fluids and the development of associated stockworks.

Known orebodies are closely associated with quartz-porphyry dacites which occur within the basalts/andesites and are surrounded by widespread propylitic and argillic alteration haloes. Hydrothermal alteration around the various orebodies is zoned and dominated by illitekaolinite- smectite with local alunite and pyrophyllite.

The sulphide mounds and related barite bodies were covered and preserved by post-mineralisation chert, gypsum, calcareous siltstone, limestone, lahars, subaqueous debris flows, volcaniclastic rocks and locally fresh dacitic lava flows at Partolang.

Gold-silver mineralisation occurs predominantly within barite-rich units, including sands, tuffs and breccias (after original dacitic rocks), which are strongly ferruginised locally. In some of the dacitic rocks, barite and hydrated iron minerals have completely replaced the host units, with original breccia textures no longer visible.

The economic copper mineralisation occurs predominantly within coherent massive sulphide units and locally in dacitic breccia units which, have been almost completely replaced by sulphides, with some minor lower-grade material occurring in fractures and as stockworks within intensely altered andesitic and dacitic tuffs and volcanics in the footwall and lateral extent of the massive sulphides. Not all massive sulphides are mineralised.

The contact between the massive sulphides, barite, footwall and hangingwall units is generally quite sharp.

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.