The deposit is a structurally controlled vein-stockwork gold-silver deposit located in the Morobe Granodiorite of the Wau Graben. Goldsilver mineralisation is contained in carbonate-adularia- quartz-sulphide 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 to moderately dipping sheeted vein swarms associated with an underlying shallow thrust.

Mining operations occur in two open pits 6km apart, Hidden ValleyKaveroi and Hamata of which Hidden Valley-Kaveroi is the largest. Both mines employ conventional open pit mining techniques with backhoe excavators and rigid dump trucks as the primary load and haul equipment. Front-end 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 generally consists of 18m inter-berm heights, blasted in 2m x 9m benches with 3m mining flitches.

Waste is disposed of in engineered valley fill waste dumps, with toes keyed in and buttressed using competent non-acid forming rock. Waste from the Hidden Valley-Kaveroi open pit is currently placed in the valley fill Western Sector and Niekywe waste dumps. A new dump, the Kaveroi Creek dump, will be built this year which, in combination with the current Western Sector dump, will provide full life of mine capacity for waste material, as well as capacity for potential extensions.

A crushing facility is located near the Hidden Valley pit with the crushed ore conveyed via a 3.8km long overland pipe conveyor. 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 4.1Mtpa of gold/silver bearing ore. The process uses a two stage crushing circuit followed by a SAG mill, gravity, CCD/Merrill Crowe circuit for silver and a carbon-in-leach circuit for the gold. A silver/gold ore bar is produced and flown off site for refining and sale.

Tailings are disposed of in a terrestrial tailings storage facility located to the south-west of the process plant. Dam-wall construction of the tailings storage facility is ongoing and largely constitutes placement of suitable oxide and fresh competent material sourced from mining in the Hamata pit and nearby quarry. The processing inventory in this ore reserve estimate is constrained by the remaining storage capacity. The Hidden Valley Extension study contemplates construction of an additional facility, TSF2.