Gold mineralisation occurs as a number of en echelon, moderately east dipping foliation parallel lodes within strongly potassic altered mafic rocks and extends over a strike length of approximately 500 m and to a vertical depth of at least 2,300 m. Four primary lodes (Main Lode, South West Branch, South Gwalia Series and West Lode) have been identified and the geometries summarised below.

Mineralisation domains are defined by abundance of quartz and quartz/carbonate veining, the presence of distinctive laminated veining (quartz/sericite/sulphides +/- au), strong potassic alteration, abundance of sulphides (commonly >3% pyrite) and elevated gold grade (>0.5g/t).

The mineralised zone strikes 15 degrees east of true north over a distance of 500m and plunges 45 degrees to the southeast. The mineralised zone consists of several stepped or en echelon style foliation parallel lodes disposed in plan in a “horse-shoe” shape with the limbs converging at the
southern end. The mineralised zone and individual lodes dip east at 35 to 45 degrees and are conformable with the foliation of the Mine Sequence mafic schists. Individual lode widths vary from 2m to 30m true width. Mineralisation has been tested to approximately 2,300m below surface and
remains open.

The primary mining method since resumption of underground production in 2008 is a Longhole Open Stoping method with paste fill. Stoping configurations are predominantly double lift (40m vertical interval) however single lift stoping (20m vertical interval) is used in some areas. The Double Lift stoping method involves concurrently mining the uphole and downhole sections of the stope. The upper and lower portions of the stope are drawn back and bogged at the same time.

All Gwalia ore is trucked to the Gwalia processing plant. The processing plant is located at St Barbara’s Leonora Operations and consists of a three-stage crushing circuit, single-stage milling circuit.

Operations and consists of a three-stage crushing circuit, single-stage milling circuit and hybrid carbon-in-leach circuit with one designated leach tank and seven adsorption tanks. Gold is recovered from activated carbon into concentrated solution via a split AARL-type elution circuit. Electrowinning and smelting are conducted in an adjacent secure gold room. The tailings from the process are thickened and pumped to a paddock-type tailings storage facility with multi-spigot distribution. Gold doré bars are transported to the Perth Mint for refining.

The technology associated with processing of Gwalia ore is currently in operation and is based on industry standard practices.

Metallurgical recovery is modelled based on the observed relationship between head grade and recovery. The average of the modelled metallurgical recovery over the Ore Reserve mine plan is 96.8%.