Mineral sands mining
EXPLORING FOR MINERAL SANDS
Mineral sands deposits are generally found on ancient coastlines like the foothills of the Australian Alps. The Glenaladale deposit was discovered through sampling areas where mineral sands may be exposed, like road cuttings, or erosion near a creek. The geologist used a gold pan to test for the presence of heavy minerals.
To define the deposit, the explorer then proceeds with several drilling campaigns. Generally, only a small drill rig is required as the deposit is sand as opposed to rock, and the depths are shallow as mineral sands mining is generally open pit and there’s no point exploring for deep mineral. Drilling one hole takes a couple of hours after which it is rehabilitated back to its original state.
MINING FOR MINERAL SANDS
Mineral sands mines are usually open pit mines that can use a range of equipment: trucks and excavators, bulldozers, scrapers, monitors and dredges. Each one of these is a very different style of mining; each with their own advantages and disadvantages. The mining method chosen depends on the nature of the deposit and the local physical environment.
Of all the dirt that is excavated, the economic minerals only account for a small volume. Most of the sand is of no value and is returned to the mine void. This means there is no hole left behind as happens with a coal or iron ore mine. Modern mineral sands mines usually rehabilitate and backfill the mine as it moves through the orebody.
Once the excavated dirt is returned to the mine pit, the area can be rehabilitated to match the original pre-mining landform. Rehabilitation is a continuous process, and can start as soon as the excavated dirt is returned to the start of the mine pit. Topsoil is replaced and vegetation cover re-seeded or replanted. In sandy soils, it is often possible to improve the soil quality by increasing the clay content of the top layer of the soil profile.
PROCESSING MINERAL SANDS
Heavy mineral sands are separated from the light sands (mostly quartz and clay) simply using gravity. The most commonly used piece of equipment for separating heavy sand from light sand are spirals.
The mined ore is mixed with water to form a slurry. The slurry is pumped to the top of a spiral. As the slurry runs down the spiral, the centrifugal force flings the lighter quartz to the outside edge, leaving the heavy minerals close to the centre of the spiral where they can be collected. Unlike some other types of mining, no chemicals are used to extract the mineral.
The collected heavy mineral is called a concentrate. The heavy mineral concentrate or HMC is then stockpiled ready for transport to a port where it is shipped to a mineral separation plant and processed into the final products.