Nickel and cobalt mineralisation at Murrin is hosted within a laterite formed from the weathering of ultramafic rocks. The resources are hosted in multiple deposits over three main project areas (North, South and East).

The nickel cobalt ore deposits of the MMN project area are positioned over serpentinised peridotite komatiitic lava flows which occur low in the stratigraphy within a sequence of felsic volcaniclastics, clastic sediments, mafic volcanics and related intrusives in the upper parts of the stratigraphic sequence. The serpentinised peridotite protolith has been folded and faulted around the Kilkenny Syncline. The sequence forms a corridor constrained by major NNE trending, westerly dipping faults.

These faults splay off the major NW trending Keith-Kilkenny tectonic zone to the SW. Gradual oxidation and leaching of the ultramafic protolith has produced a regolith with sub-horizontal layers which hosts the ore deposits (Saprolite 2020).

The MMN Project is located within the Mt Morgan district of the Mt Margaret mineral field between Leonora and Laverton (Coffey 2020). The regolith profile can be broadly divided into five main geological units produced through lateritic weathering.
1. UM: the basal unit is slightly weathered locally silicified ultramafic that grades upward into saprolite;
2. SA: saprolite zone, commonly magnesium and silica rich;
3. SM: smectite is the main nickel bearing unit of the profile;
4. FZ: ferruginous zone, dominantly comprised of kaolinite Fe oxides (typically hematite), commonly silica-rich and capped with colluvium;
5. The uppermost unit consists of colluviums and mixed chlorite-kaolinite plastic clays, referred to as the mottled zone (Coffey 2016).

Ultramafic regolith profiles are commonly bound by weathered felsic and/or mafic volcanic and intrusive rock. The original terrain around the 17 Series Inpit TSF grades to the south-west. The highest point is at the north-eastern tip (approximately +467m RL) from which ground levels gradually reduce to about +451m RL at the south-western tip (Coffey 2020).

Economic mineralisation at the Murrin Murrin Ni-Co project is contained within the weathered profile of the ultramafic protolith. As a result, the mined pits rarely expose the fresh ultramafic rock to allow for detailed investigations of the structural features of the deposit. However, as these structural features have acted as conduits for fluid flow or as areas of increased permeability during the formation of the laterite profile, they tend to be revealed in the distribution of certain elements in the regolith profile (Coffey 2020).

The operation at Murrin Murrin consists of:
- Open-pit nickel-cobalt mining operations at Murrin Murrin North, Murrin Murrin South and Murrin Murrin East;
- Calcrete quarrying operations at the Windarra Calcrete Quarry.

Murrin Murrin mines approximately 4.5 million tonnes (t) of nickel laterite ore per year. The operation uses open-pit mining techniques.

Bis provides a range of mining and processing services to Minara Resources’ nickel mine and processing facility at Murrin Murrin.

Key responsibilities across the full value chain include:
- drilling, blasting, crushing and rehabilitation work
- off-road load and haul of nickel ore and calcrete
- on-road load and haul of bulk goods, chemicals and finished product
- calcrete mining; and maintenance of the haul road and Bis fleet

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The operation Murrin Murrin processes the ore using High Pressure Acid Leaching (HPAL) to recover the nickel and cobalt from the laterite ore.

The laterite ore mined at Murrin Murrin is recovered through shallow, open cut mining methods and transported via multiple roads to the Murrin Murrin hydrometallurgical processing plant where it is delivered to the run of mine (ROM) pad.

Here, the ore is sorted according to grade, crushed and blended to ensure consistent feed into the plant’s ore feed preparation circuit.

The HPAL circuit consists of four titanium lined autoclaves, each the size of a small submarine.

The nickel and cobalt is leached out of the ore slurry, grading approximately 1.3% nickel and 0.09% cobalt, and into solution, by raising the pressure up to 44 atmospheres and mixing it with highly concentrated sulphuric acid at a temperature of 255 degrees celsius. This generates substantial quantities of heat which is recovered and then used to pre-heat incoming slurry. Now that the nickel and cobalt have been leached and are subsequently in soluble form, they must be separated from the residue waste material. This solution is "washed" to remove the waste residue, allowing the valuable nickel and cobalt solution to move forward for further processing, and the residue to be neutralised for tailings disposal as inert waste.

Leached ore solution now passes into the neutralisation circuit where calcrete is added to neutralise the acid. The solution is then passed into the mixed sulphides precipitation circuit, where hydrogen sulphide gas is added to convert the solution into a mixed nickel and cobalt sulphide precipitate.

The mixed nickel and cobalt sulphide enters another autoclave where pure oxygen converts the solids from a mixed sulphide into a metal sulphate solution. Impurities such as iron and zinc are then removed, before the cobalt and nickel are separated using solvent extraction.

The nickel sulphate solution then enters six parallel autoclaves, known as the hydrogen reduction circuit, where the hydrogen is added, nickel metal is precipitated and then separated from the nickel free liquid stream. The nickel powder is then dried before entering the final processing stage.

The powder is formed into a pillow-shaped briquette, sintered in a furnace and then packaged for transportation. The entire process from beginning to end takes approximately 14 days. Murrin Murrin produces nickel and cobalt briquettes that easily meet the highest A Grade standards of the London Metals Exchange and are highly regarded and in strong demand from consumers around the world.

The cobalt sulphate solution from solvent extraction follows a separate processing path which is similar to the nickel processing path but on a smaller scale.

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