Porgera Mine is an epithermal vein-type gold-silver deposit but it shares many characteristics with porphyry copper deposits. Remnant heat from the intrusive rocks drove the boiling and upward migration of hydrothermal fluids and resulted in the emplacement of mineralization. The movement of these fluids was controlled by permeability of the rock mass, which developed in and around faults and tectonic zones of dilatancy. As such, the mineralization tends to occur in tabular bodies and breccia zones, the geometry of which is strongly influenced by the orientation of fault structures and subsidiary fractures. Deposition of ore minerals in epithermal systems is also dependent upon temperature and hydrostatic pressure. These conditions are generally closely related to elevation, with reduction of both temperature and pressure as the fluids migrate upwards.

The Porgera Joint Venture is an open pit and underground gold mine located at an altitude of 2,200- 2,600 meters in the Enga Province of Papua New Guinea.

The Open Pit mine is 500 meter deep, below the highest point of surface topography and approximately 30 million tonnes (t) of ore per year is excavated. The material mined is a combination of gold bearing ore and barren waste.

Pit dimensions: 2.0km long x 1.2km wide x 400m deep.

Mining in the open pit is undertaken on 10 meter high benches. When the material is too hard to be free dug, the rock is drilled and blasted with a range of drill patterns to suit the litholog.

The Open Pit is a conventional truck and shovel operation and is serviced by a large modern mining fleet of 175t and 90t haul trucks, loaded by 200t and 120t shovels and excavators. There are also smaller 40t and 35t excavators for ancillary work.

The Porgera Underground Mine is a modern, trackless mine, producing approximately 1.4 million tonnes of ore per year from three primary production areas: North Zone, East Zone and AHD.

The underground (UG) operation mines the lodes at depth currently up 330 meter beneath the current pit floor. The Underground operation has a strike extent of approximately 1.6 kilometer (km). The primary access is via a twin decline system from surface with secondary internal accesses connecting the various mining areas.

Mining is done by convention long hole open stoping. Drives are developed along the strike of the lenses at 15m vertical intervals with long-hole stoping used to extract the ore between these levels.

The voids generated by mining are back-filled with a combination of paste and co-paste disposal to enhance ground stability and allow maximum extraction of ore.

The UG mine operates on a modern trackless mining fleet consisting of CAT 2,900 loaders, 45t and 55t capacity haul trucks and supporting drills and auxiliary equipment.

Ore is processed in a complex minerals processing plant. The open-pit and underground mines supply both course gold and refractory ore to a processing plant that includes crushing, grinding, gravity recovery, flotation, oxidation (autoclave) and Carbon In Pulp (CIP) circuits to produce a gold dore product and a high grade pyrite concentrate for shipment to offsite refineries and smelters for final processing.

The major components on the Porgera processing plant include:

- crushing circuit and coarse and fine ore storage;
- grinding circuit;
- gravity and regrind circuit;
- flotation circuit;
- pressure oxidation and tailings neutralisation circuits;
- leaching and adsorption circuits;
- acid wash and stripping elution circuit;
- electrowinning and gold refinery;
- oxygen plant;
- chemical storage and mixing;
- cyanide destruct plant; and
- tailings pipework and infrastructure.

Run-of-Mine (ROM) ore ........