Mt Cattlin — 2023 Technical Report (Stage 4 Expansion)

The report describes the processing plant configuration and historical modifications at the Mt Cattlin operation through 2023.

Report context

This technical report for the Mt Cattlin project, dated 2023, documents the processing plant located approximately 2 km northwest of Ravensthorpe, Western Australia. The plant has undergone several modifications since operations commenced in October 2010, with throughput targets increasing from 1 million tonnes per annum originally to 1.8 million tonnes per annum under the Yield Optimisation Project that began in 2019.

Processing route

Early Operations (2010–2016)

The original plant consisted of a four-stage crushing circuit producing a -6 mm product from ROM ore at a treatment rate of 1 million tonnes per annum. The crushing plant ran on day shift only, providing feed to an ore bin, which fed the concentrator on a continuous 24-hour basis.

The concentrator included a reflux classifier for mica removal and dual size stream, two-stage Dense Medium Separation (DMS) cyclones. Final spodumene concentrate was stacked on a pad adjacent to the plant area, drained, and hauled by road to Esperance Port for bulk shipment. Coarse waste DMS plant float material was conveyed to a Rejects Load Out Bin and hauled by truck to mined portions of the pit for backfill or road base.

DMS pre-screen undersize (-0.5 mm) was treated by gravity separation using spiral classifiers and shaking tables to recover a tantalite concentrate, which was contract dressed and sold, or stockpiled depending on price. Tantalite circuit tailings and other plant spillage streams were directed to a thickener for process water recovery, with thickener underflow pumped to the tailings storage facility approximately 500 m north of the plant.

Operations (2016–2018)

In 2016, process modifications were implemented targeting an increased processing throughput of 1.6 million tonnes per annum of ROM ore. Significant changes included: change from 4-stage to 3-stage crushing; change of crusher top size from -6 mm to -12 mm; modified wet screen to cut at 1 mm; other size fraction changes for spirals and DMS plant; addition of reflux classifiers and a vacuum belt filter following the spirals to recover product from wet screen undersize; and DMS reflux classifier used only for the fine size fraction of DMS feed.

Yield Optimisation Project (2019–Present)

Beginning in 2019, additional improvements were made as part of the Yield Optimisation Project, designed to improve yield and increase throughput of ROM ore to 1.8 million tonnes per annum. These changes included: further optimisation of size fractions for wet plant feed and DMS plant feed; a reliberation circuit for secondary DMS rejects to recover spodumene composited with gangue material; replacement of the vacuum belt filter with Wet High Intensity Magnetic Separation and an ultrafine DMS circuit for spodumene recovery from wet screen undersize; and introduction of a Product Quality Upgrade circuit containing a Wet Belt Magnetic Separator and an optical sorter for basalt removal to improve product grade. The Product Quality Upgrade circuit was shutdown in 2021.

In early 2019, two in-series optical sorters were introduced in the crushing circuit to utilise material previously classed as contaminated and not suitable for plant feed. Subsequent optimisation allowed for parallel sorter operation and increased processing rates, producing plant feed from previously unsuitable contaminated basalt material.

ROM Pad and Crushing Circuit

Ore from the mine is stockpiled on the ROM pad based on Li₂O grades and basalt content. A visual classification between clean and contaminated ore is made by ore spotters in the pit. Clean ore contains less than 3% by weight basalt and is hauled to the ROM for crushing. Contaminated ores with basalt contents estimated between 3% and 30% are directed to a separate area on the ROM for primary crushing to -100 mm and additional beneficiation by optical sorting prior to rejecting the majority of basalt from plant feed.

Clean ore is reclaimed from the ROM stockpile or optical sorter product pile by front end loader and fed into the ROM Bin, passing over a grizzly feeder into a single toggle jaw crusher. Material coarser than 125 mm feeds the jaw crusher and progresses to the secondary crushing stage. Grizzly undersize passes directly onto a triple-deck sizing screen producing secondary crusher feed (+50 mm), tertiary crusher feed (-50 to +14 mm), and -14 mm material reporting to the Fine Ore Stockpile or Fine Ore Bin. The Fine Ore Bin has nominal capacity of 2,500 tonnes and directly feeds the main wet plant.

Contaminated ore is batch processed through the crushing circuit, with secondary crusher product and -50 +14 mm screen product directed towards two parallel triple-deck sizing screens feeding optical sorters and tertiary crushers. The sizing screens use 40 mm, 22 mm, and 14 mm apertures respectively to separate feed for optimum contaminant rejection. The +40 mm fraction reports to optical sorters where contaminant basalt is removed. The +40 mm optical sorter product and -40 +14 mm material progress to the tertiary crusher, and -14 mm reports to the Fine Ore Stockpile.

Wet Plant Feed Classification

Ore from the Fine Ore Bin is fed over a wet screen with oversize, nominally +2.0 mm, dewatered and conveyed to storage Bin 10 and then control fed to the DMS plant. Screen undersize (-2.0 mm) material is collected in a hopper and pumped to the fines circuit.

Fines Circuit

The fines plant receives approximately 15% of total feed, split into coarse (+710 µm to 2.0 mm) and fine (less than 710 µm) streams by Derrick Stack Sizer screens. The coarse stream is pumped directly to coarse spiral concentrators. Fines material is pumped to deslime cyclones ahead of fines spiral concentrators.

Concentrate from both coarse and fines spirals combines on a single Wilfley shaking table to separate the tantalite product for bagging and dispatch, with table concentrate averaging approximately 5% Ta₂O₅ collected in one-tonne bulk bags.

Fine spirals waste material is transported via the thickener to tailings, while coarse spirals product material is transported to the ultrafine circuit for further spodumene recovery.

Ultrafines Circuit

Coarse spirals waste is pumped to a wet high intensity magnetic separator. Magnetic material is sent to rejects, while non-magnetic material is fed to a reflux classifier for mica removal. The mica-containing stream is pumped to the tailings thickener. Classifier underflow is dewatered by a screw feeder and fed to the ultrafine DMS feed bin.

Ultrafine DMS feed is added to a ferrosilicon slurry and pumped through the ultrafine DMS cyclone cluster, producing underflow of spodumene concentrate (sinks) and overflow of reject material (floats). Ferrosilicon is recovered from both sinks and floats via sieve bends followed by magnetic separation. The density of ferrosilicon slurry is maintained by pumping a portion through primary and secondary densifying cyclones, with fresh ferrosilicon added when required.

The ultrafine DMS floats are pumped to a dewatering screw and fed onto the rejects conveyor. Sinks are combined with concentrate from the main DMS plant and report to final product. The ultrafine DMS product is generally slightly lower grade, making up about 2–3% of total recovery.

Key reported parameters

Technical qualifications

The report documents historical operating configurations and process modifications through 2023 but does not provide currently achievable throughput rates, metallurgical performance data, or economic parameters for the Stage 4 Expansion. The processing description is based on the flowsheet as summarised in Figure 17-1 of the report and associated text. Particle size specifications and equipment configurations show the plant state at the time of the technical report.

Source: Mt Cattlin , 2023 Technical Report (Stage 4 Expansion), Section 17 Recovery Methods.