The Nyngan scandium resource is located within a limonitic and saprolitic tertiary age laterite profile, covered by 12 to approximately 25m of Cainozoic alluvium. A fairly typical laterite profile is developed at the prospect:
-Hematitic clay.
-Limonitic clay.
-Saprolitic clay.
-Weathered bedrock.
-Fresh bedrock.

A geological interpretation plan has been previously prepared, based on bedrock intersections in both recent and previous drilling. Because of the weathered nature of the drill cuttings, the geological plan must be considered interpretive. The igneous rock types which have been encountered are:
Pyroxenite.
-Olivine Pyroxenite.
-Hornblende Pyroxenite.
-Hornblendite.
-Magnetite Pyroxenite.
-Dunite.
-Monzonite.

There is a suggestion of a layered trend of the complex in a NW-SE direction (this is supported by the magnetic pattern). These trends reflect a broadly concentric zonation of lithologies (mafic lithologies in the centre becoming intermediate in moving out from the “core”) in the complex. There also appears to be a zone of stronger alteration in the (south) centre of the zone where abundant magnetite and mica (phlogopite) occur.

All earthworks will be carried out using a mining contractor on a campaign basis, and mining will be carried out using selective truck and excavator mining methods. Campaigns will typically be conducted three times each year for the 20 year mine life.

The process plant for the Nyngan Scandium Project will treat the scandium bearing limonite mineralisation from Nyngan to produce a scandium oxide product. The flowsheet consists of:

Recovery of ore from mined stockpiles using a front end loader. Adding the mill feed to a hopper and then onto a conveyor. The lightly crushed mineralisation then is slurried with process water in the drum scrubber and then into a trommel screen. The slurry from the trommel screen underflow falls into a hopper and is pumped to the ball mill circuit, via the cyclone feed hopper, in order to further break up clay material. The trommel screen overflow is stockpiled as coarse rejects.

The slurry from the ball mill discharges into the cyclone feed hopper and then pumped to a series of cyclones. Cyclone overflow passes to the leach feed thickener. Cyclone underflow (+75 µm) is returned to the feed chute of the ball mill.

The leach feed thickener increases the solids density in the underflow to 38% solids. Leach feed thickener overflow is returned to the ore preparation circuit via the leach feed thickener overflow tank and associated pumps. The leach feed thickener underflow is pumped to the HPAL feed storage tanks.

Leach feed thickener underflow is combined with a proportion of the returned solvent extraction raffinate (approximately 20% of the raffinate stream) in one of two HPAL feed slurry storage tanks to achieve the nominal feed solids density of 30% into the autoclave.

Feed from the HPAL feed slurry storage tanks is passed through the HPAL feed slurry heater where it is heated in a heat exchanger with excess high pressure splash steam.

Preheated HPAL feed slurry is further heated in three stages of splash vessels using flash vessel vent steam before being pumped with high pressure pumps into the autoclave, where additional HP steam is added to raise the temperature to 265°C. Concentrated sulphuric acid is also added to the autoclave with a high pressure pump. Slurry density inside the autoclave is designed at 25% solids.

The slurry is depressurised in three stages of flash vessels with letdown steam recirculated back to the corresponding splash vessels. Any excess steam is vented to atmosphere via the HPAL vent scrubber.

The leach slurry, containing the dissolved scandium, is passed through an eight stage counter current decantation (CCD) circuit to wash the entrained scandium from the leach residue. The wash solution is a mixture of raw water, solvent extraction raffinate and dirty condensate streams from the flash vessels and preheateThe pregnant solution from the CCD circuit containing the scandium is cooled, filtered in one of two sand filters and sent to solvent extraction for recovery of the scandium.rs.

Solvent extraction of scandium occurs by contacting the PLS with an organic phase containing a primary amine (Primene JM-T) dissolved in a kerosene (Shellsol D70) in three counter current extraction stages. A scandium sulphate complex ion leaves the aqueous phase and loads onto the amine. The organic phase is then washed with a dilute sulphuric acid scrub solution.

Stripping the scandium from the Primene JM-T is conducted by contacting the loaded organic phase with a hydrochloric acid solution, boosted with extra chloride salt addition. The scandium enters the aqueous strip liquor as a scandium chloride complex ion.

The stripped organic is regenerated with dilute sulphuric acid solution before being recirculated back to the extraction stages. The loaded strip liquor is filtered through a garnet anthracite filter and then a carbon column before being heated to 65°C in the LSL tank. Solution from the LSL tank is withdrawn in 6 m³ batches on day shift operations and the scandium is precipitated by adding oxalic acid solution to the tank and stirring for 15 minutes.

The scandium oxalate precipitate is filtered in a plate and frame filter press. The scandium oxalate is added to rotating kiln furnace and calcined to scandium oxide at 900°C, before being washed with deionised water and filtered. The scandium oxide is then dried and dispatched in small security drums.

The residual slurry from the CCD circuit is partially neutralised with lime slurry to pH 2 and then sodium hydrosulphide (NaHS) is added to convert any Cr (IV) in solution to Cr (III). More lime slurry is added in two stages to raise the pH to 9 in order to precipitate any heavy metal ions from solution.