The deposit is a structurally controlled vein stockwork gold-silver deposit located in the Morobe Granodiorite of the Wau Graben. Gold silver mineralisation is contained in carbonate-adularia-quartzsulphide vein stockworks and in a few instances in hydrothermal breccias. Discrete zones of intense stockwork fracture and mineralised veining comprise individual lodes. At the Hidden Valley deposit gold and silver are related to steeply dipping (Kaveroi Creek Zone) and flatlying (Hidden Valley Zone) sheeted vein swarms associated with an underlying shallow thrust.

Mining operations occur in two open pits 6km apart, Hidden Valley and Hamata of which Hidden Valley is the largest. Both mines employ conventional open pit mining techniques with back-hoe excavators and rigid dump trucks as the primary load and haul equipment. Frontend loaders are used for crusher feed and stockpile reclaim. A number of articulated smaller dump trucks are used for construction, and to a lesser extent mining in Hamata.

Mining bench configuration consists of 18 m inter-berm heights, mined as 3m x 6m benches of 2m x 3m flitches (in ore).

Waste is disposed of in engineered valley fill waste dumps, with toes keyed in and buttressed using competent non-acid producing rock. This waste is currently captured in the Western Sector dump which is nearing its fill capacity. The construction of the next dump, Neikywe, is underway with the pushdown ramp, underdrains, and toe construction. Neikwiye Valley dump will provide the waste rock capacity for the remainder of the Stage 6 Reserve.

Crushed ore is conveyed from the Hidden Valley pit via a 3.8km long overland pipe conveyor (OLC). Ore from the Hamata pit is trucked to the Hamata crushing station, located next to the ore processing plant.

The Hidden Valley process plant was designed to treat nominally 4.2Mtpa of gold/silver bearing ore. The process uses a two stage crushing circuit followed by a SAG mill, gravity, CCD/Merril Crowe circuit for silver and carbon in leach circuit for the gold. A silver/gold dore bar is produced and flown off site for refining and sale.

Tailings are disposed of in a terrestrial tailings storage facility (TSF) located to the South-West of the process plant. Dam-wall construction of the TSF is ongoing and largely constitutes placement of suitable oxide and fresh competent material sourced from mining in the Hamata pit. The processing inventory in this Ore Reserve estimate is constrained by remaining TSF capacity at ~26Mt. Construction of an additional facility is under study to accommodate resource growth strategies.