The mineral sand deposits occur at the top of a series of sedimentary deposits, within a sequence of relatively recent unconsolidated sands.

They generally originate from the adjacent Yilgarn Block, which has been eroded, transported by rivers and streams and deposited as beach sands along former coastlines.

The deposits now form successive north-south linear deposits well inland from the present coast. Upper level deposits that either outcrop or are covered by minimal amounts of nonmineralised material (overburden), occur in the northern half of the tenement. Mid-level deposits are covered with varying depths of overburden. The basement deposits occur below the mid-level deposits and are typically more weathered and of lower heavy mineral grade.

Cooljarloo is 170 kilometres north of Perth, where the company produces heavy mineral concentrates from dredging and dry mining operations.

The dredging operation uses one of the world’s largest floating dredges in a purpose-built pond to pump slurried ore at a rate of 3,000 tonnes per hour to a floating concentrator which recovers heavy minerals from the sand and clay using a series of gravity spirals. The heavy mineral concentrate produced at Cooljarloo is transported south in specially designed road trains to Tronox’s Chandala Processing Plant for separation and processing.

As mining operations move through the orebody, sand and clay are returned to fill the void and the surface is contoured to landforms similar to those that existed prior to mining. Because less than 5% of the total sands mined are removed during mining, the rehabilitation program can establish similar landforms and ecosystems to the original countryside.

Performance
The dredging operation at the south mine excavates the deeper deposits located below the water table.

A contract overburden removal fleet handles an average of 2.5 million bulk cubic m (BCM) of overburden per annum. The overburden is generally between 2-15 metres thick. Equipment used to remove this overburden includes one Komatsu PC2000 250 tonne excavator with a fleet of four Caterpillar 777D 100 tonne dump trucks. The Komatsu excavator can move up to 800 BCM/hour.

Two dredges operate in a pond up to 25 m deep and mine ore between 22 and 30 m thick. Together they mine 24 million tonnes of ore per year, which is delivered to the shared Wet Processing Plant. The pond water is natural groundwater and is fresh. The pond is up to one k long and 400 m wide. These facilities are controlled by operators via computers and GPS satellite navigation.

HMC is pumped to a central stockpile where it is stacked, ready for rehandling into road trains for transport to our processing facility at Chandala. Tailings from the plant comprise washed sand and clay at 2,950 tonnes per hour. The tails are directed either via a float line and floating tails stacker back to the dredge pond to form stable beaches and return stripped overburden or sent via external tails pipelines up to six kilometres in length to backfill previously mined out pits.

Clay from the ore is dried in purpose-built cells on the mined pits and on future mine path. No chemicals are used in the process.

Northern Operations complex in Western Australia is consisted of the Cooljarloo dredge mine and floating heavy mineral concentration plant and the Chandala metallurgical site which includes a mineral separation plant and a synthetic rutile plant that produces synthetic rutile.

Two dredges in a single pond feed an ore slurry to a floating concentrator to produce HMC, which is hauled by trucks 110 km south to our Chandala metallurgical complex near Muchea, 60 km
north of Perth, for the recovery of ilmenite, rutile, leucoxene and zircon. Ilmenite is upgraded at Chandala to SR, a high-TiO2 feedstock for our Kwinana and other TiO2 pigment plants.

Processing - Both wet and dry mining techniques utilize wet concentrator plants to produce a high grade of heavy mineral concentrate (typically approximately 90% to 98% heavy mineral content). Screened ore is first deslimed, a process by which slimes are separated from larger particles of minerals, and then washed through a series of spiral separators that use gravity to separate the heavy mineral sands from lighter materials, such as quartz. Residue from the concentration process is pumped back into either the open pits or slimes dams for rehabilitation and water recovery. Water used in the process is recycled into a clean water dam with any additional water requirements made up from pit dewatering or rainfall.

Mineral Separation - The non-magnetic (zircon and rutile) and magnetic (ilmenite) concentrates are passed through a dry separation process, known as the “dry mill” to separate out the minerals. Electrostatic and dry magnetic methods are used to further separate the ilmenite, rutile and zircon. Electrostatic separation relies on the difference in surface conductivity of the materials to be separated. Conductive minerals (such as ilmenite, rutile and leucoxene) behave differently from non-conductive minerals (such as zircon) when subjected to electrical forces. Magnetic separation techniques are dependent on the iron content of a mineral. Magnetic minerals (such as ilmenite) will separate from non-magnetic minerals (such as rutile and leucoxene) when subjected to a magnetic field. A combination of gravity and magnetic separation is used to separate zircon from the non-magnetic portion of the heavy mineral concentrate.