Rosemont gold deposit is hosted in a quartz dolerite zone of a dolerite sill intruding ultramafic and argillaceous sedimentary units of the western limb of the Erlistoun Syncline in the Duketon Greenstone Belt.

Gold mineralisation is associated with brittle fracturing and quartz albite sericite carbonate sulphide alteration within the quartz dolerite. Most gold occurs below the weathered profile in saprock and fresh rock with the upper saprolite being leached of gold.

The mineralisation trends NNW over a strike length of 4.9km and dips steeply to the east and west, varying along strike.

The geology at Rosemont has gold hosted in a steeply dipping quartz-dolerite unit intruding into a mafic-ultramafic sequence. Gold mineralisation is within a brittle quartz-dolerite phase of the Rosemont Dolerite, primarily occurring within discrete, steeply dipping, quartz-dolerite paralleled, en-echelon and stacked vein structures. The quartz-dolerite varies from 5 metres, up to 100 metres wide.

The mining method assumed in the Ore Reserve study is the same as that currently employed at the Rosemont Gold Mine, which utilises drill and blast, excavator and truck open pit mining. The existing pit has been designed to be developed in a series of progressive cutbacks. The Ore Reserve pit is designed as a further series of extensional cutbacks to the existing pit.

Geotechnical and hydrogeological recommendations have been applied during pit optimisation and incorporated in design with ongoing reviews. Mining dilution and ore loss factors have been dealt with in the estimation of the OK Mineral Resource.

The existing Rosemont crushing and grinding Plant and the Garden Well CIL Processing facility will be utilised to treat the Ore Reserve and a recovery factor of 94% has been assumed in the estimation of the Ore Reserve.