Mount Saddleback is the highest peak in the

Darling Range The Darling Scarp (), also referred to as the Darling Range or Darling Ranges, is a low escarpment running north–south to the east of the Swan Coastal Plain and Perth, Western Australia. The escarpment extends generally north of Bindoon, West ...

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

. It is found at the easternmost part of the Darling Range about south of Boddington and west of Williams.

Bauxite Bauxite () is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (), boehmite (γ-AlO(OH)), and diaspore (α-AlO(OH) ...

is mined on the flanks of the peak and processed at

Worsley Alumina Worsley Alumina comprises a bauxite mine located near the town of Boddington and an Alumina refinery located near Worsley. Ore is mined then transported to the refinery via an overland conveyor system. Alumina is then transported to the port ...

which has been in operation since 1984. The entire range is formed by the Darling Fault, a fault that has been moving continually through its long history with the last major activity occurring 135 million years ago when Australia broke away from the super continent,

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

. The Darling Scarp formed around 570 million years ago and is composed of 3700 million-year-old rocks that are mostly

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...

. Saddleback is found on the eastern side of the fault on the Darling Plateau. The underlying bedrock is composed of medium grained granite and sometimes

Archean The Archean ( , also spelled Archaean or Archæan), in older sources sometimes called the Archaeozoic, is the second of the four geologic eons of Earth's history of Earth, history, preceded by the Hadean Eon and followed by the Proterozoic and t ...

aged granitoids. The surface of the mount is an iron-rich hard cap with a thickness of around containing 40 to 50% Fe₂O₃ including significant amounts of quartz sand. Below this is an Aluminium oxide enriched interval with clay rich base, with an average depth of and a maximum of up to . Below this is a transition zone primarily made up of

kaolin Kaolinite ( ; also called kaolin) is a clay mineral, with the chemical composition Al2 Si2 O5( OH)4. It is a layered silicate mineral, with one tetrahedral sheet of silica () linked through oxygen atoms to one octahedral sheet of alumina (). ...

clays followed by weathered bedrock. Above the bedrock the soils are composed of 25–30% bauxite with irregular and lenticular-shaped ore bodies. The largest ore body contains over an area of with many smaller bodies. The total estimated reserve of bauxite in the mining area is .

References

{{reflist Saddleback Darling Range Mining in Western Australia