Higginsville is located almost entirely within the well-mineralised Archean Kalgoorlie Terrane, between the gold mining centres of Norseman and Saint Ives. The Archaean stratigraphy has a general northward trend comprising multiply deformed ultramafic – gabbro – basalt successions adjoined by sediments to the west and east. Shearing and faulted contacts are common. The units have been structurally repeated by east over west thrust faulting.

The majority of gold mineralisation projects along the Trident line-of-lode and is hosted by Poseidon Gabbro and high MgO dyke complexes. Mineralisation is hosted within or marginal to quartz veining and is structurally and lithologically controlled. Higginsville is also host to significant palaeochannel mineralisation. Mineralised zones comprise both placer gold, normally near the base of the channel-fill sequences, and chemically- precipitated secondary gold within the channel- fill materials and underlying saprolite. These gold concentrations commonly overlie, or are adjacent to, primary mineralised zones within Archaean bedrock.

The HGO can be sub-divided into six major geological domains:
- Trident line-of-lode;
- Chalice;
- Lake Cowan;
- Southern palaeochannels;
- Mount Henry; and
- Polar Bear Group.

Trident line-of-lode
The majority of mineralisation projects along the Trident line-of-lode are hosted within the Poseidon Gabbro and high-MgO dyke complexes in the south. The Poseidon Gabbro is a thick, weakly- differentiated gabbroic sill (Newman et. al., 2005), which strikes north south and dips 60° to the east, is over 500m thick and 2.5km long. The gabbro is broadly zoned (Zones 1 - 5), with Zone 3 considered the most favourable for mineralisation: - Zone 1 is interpreted as an ultramafic cumulate base;
- Zone 2 is a feldspar-phyric mafic unit;
- Zone 3 is an equigranular, feldspar-quartz phyric unit.
- Zone 4 is a bladed amphibole unit; and
- Zone 5 is an equigranular, feldspar-amphibole phyric unit.
Faulting and shearing are important geological features in the region, with the Poseidon Thrust comprising a 5 to 10m wide mylonite zone, which marks the contact between the eastern sedimentary packages of the Black Flag Beds and the underlying Paringa Basalt.

A number of shallow, east-dipping, reverse fault zones have also been intersected in both the Trident underground mine and the Poseidon open pit. These structures vary in thickness between 5 and 50m, and are generally moderately to well mineralised. Vertical to sub-vertical (steep east and steep westdipping), north to northeast striking shear zones are evident throughout the Trident deposit, and are thought to form a primary control and fluid source for mineralization.

In the south deposits such as Fairplay North East and Corona are hosted by high-Mg basalts which strike North-South and dip at 50°- 60° to the east. Thrust over the basalts are thick sequences of metasediments (Black Flag Beds) comprising fine grained, laminated to massive epiclastics tending to be more arenaceous and quartz rich to the east.

The mineralisation is hosted within or marginal to quartz veining and is structurally and lithologically controlled. Veins occur on and adjacent to the thrust contact and may be up to 3m in width and lie preferentially in the basalt host. Alteration consists of silica flooding which has obscured older textures; locally intense biotite alteration within the basalts closely associated with the silicification and arsenopyrite alteration is common and locally intensified with the quartz veining and silica- biotite alteration.

Chalice
The Chalice deposit is located within a north south trending, 2-3km wide greenstone terrane, flanked on the west calc-alkaline granitic rocks of the Boorabin Batholith and to the east by the Pioneer Dome Batholith. The mafic-ultramafic rocks of the greenstone terrane comprise upper greenschist to middle amphibolite facies metamorphosed, high-magnesium basalt, minor komatiite units and interflow clastic sedimentary rocks intruded by a complex network of multi- generational granite, pegmatite and porphyry bodies.

The dominant unit that hosts gold mineralisation is a fine grained, weak to strongly foliated amphiboleplagioclase amphibolite, with a typically lepidoblastic (mineralogically aligned and banded) texture. It is west-dipping and generally steep, approximately 60°-75°. It is typically more competent than the ultramafic unit. The amphibolite is of basaltic derivation, with alteration and the metamorphic grade generally increasing markedly towards the main mineralization zone.

Lake Cowan
The area is situated near the centre of a regional anticline between the Zuleika and Lefroy faults, with
the local geology of the area made more complex by the intrusion of the massive Proterozoic
Binneringie dyke.

The Binneringie dyke varies locally from a hornblende dominated dolerite to a feldspar dominated granodiorite, is medium to coarse grained, and is complexly interrelated to the mineralised structures in the Lake Cowan area. In a break of form for these generally east-northeast – west-southwest trending dyke systems, at Lake Cowan the Binneringie dyke follows the deep seated crustal weaknesses north and south for some distance, in the process interfering with the pre- existing mineralisation on a large scale. The majority of mineralisation at the Lake Cowan Mining Centre is hosted within an enclave of Archaean material surrounded by the Binneringie dyke.

Southern Palaeochannels
Throughout the Higginsville Gold Operations, a significant proportion of gold deposits are hosted by sediments within the Southern Palaeochannel network. Mineralised zones comprise both placer gold, normally near the base of the channel-fill sequences, and chemically-precipitated secondary gold within the channel-fill materials and underlying saprolite.

Two main palaeochannel systems exist at Higginsville:

- Mitchell palaeochannel system – This includes the existing pits of Graveyard North, Graveyard, Aphrodities and Mitchell. Mitchell 3 and 4 remain unmined and are located to the south of the existing Mitchell pit.

- Challenge / Swordsman palaeochannel system – Which includes existing pits - Bullseye, Venus, Jupiter, Saturn, Neptune and Pluto. The areas of Mars (south of the Venus pit) and the southern extension of Pluto remain insitu (unmined).

Both palaeochannel systems get deeper towards the south (which suggest the flow direction of the ancient rivers) and flow into Lake Cowan.

The only active mining operation is the Baloo open pit at HGO.

Baloo is a deposit situated within Lake Cowan and is situated approx. 1km from the nearest shore line. The mineralisation is covered with lake alluvium with inconsistent stability characteristics. Access to the deposit will need to be established which has sufficient strength to provide a stable haul road for the mining activities.

A 35m deep initial pit has been designed which targets the oxide portion of the resource preferentially. The design configuration suits a 120t class excavator and 90t tonne payload rigid dump trucks.

Gold mineralization is processed at the RNC-owned Higginsville Gold Mill. Material is processed in either batches or mixed with other mineralisation sources from Higginsville. The Higginsville Mill flowsheet is a conventional CIP gold circuit with quaternary crushing and ball milling with a gravity recovery circuit on the cyclone underflow. Grinding is followed by leaching with a production capacity of 1.3Mtpa. The gravity recoverable gold from the mineralization, which is recovered through a Knelson concentrator and Acacia high intensity leach reactor is treated separately to produce bullion. The mill cyclone overflow product flows to a leach circuit. The pregnant solution reports to carbon adsorption tanks followed by an acid wash and elution before the electrowinning circuit produces a calcine for smelting.

There are several approved tailings storage facilities on site, and currently the tailings are being deposited in the exhausted Fairplay East open pit until Q3 2019, after which deposition will be transferred to alternate open pits located on site. There is also a four paddock tailings storage facility that could be used in the future if required with additional dam lifts or expansions.