Darling Range Bauxite
Bauxite was recognised in the Darling Range in Western Australia as early as the 1890s. However, this was not confirmed until 1957 when exploration by Western Mining Corporation found significant bauxite deposits in the area. A joint-venture company was set up to develop an integrated alumina industry, of which the Aluminium Company of America (now Alcoa Inc.) became a partner. A 12,619 sq km bauxite mining lease in the Darling Range was granted to the joint venture in 1961. Leases containing bauxite deposits peripheral to the Alcoa of Australia Ltd's lease were obtained by what eventually came to be known as Worsley Alumina.
Darling Range bauxite is a low-grade ore with around 27-30 percent aluminium oxide. Deposits typically consist of half a metre of topsoil and overburden, which is removed and conserved for later rehabilitation. The caprock bauxite (generally 1 to 2 metres) is drilled and blasted before extraction with the more friable bauxite below. It is the lowest grade ore mined on a commercial scale anywhere in the world, requiring substantial investment in a fleet of loaders, excavators and trucks as well as crushing and conveying equipment.
The Darling Range bauxite, once thought to be a uniform lateritic blanket, is in fact a complex regolith varying in thickness from 0 to 100mm that has formed in situ, thus preserving features of the parent rock less susceeptible to erosion (eg dolerite dykes). Understanding the variations in the regolith will aid in the application of mine rehabilitation techniques and is the subject of current research.