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, to th ...

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to ...

. 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 (Al(OH)3), boehmite (γ-AlO(OH)) and diaspore (α-AlO(O ...

is mined on the flanks of the peak and processed at Worsley Alumina 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, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final st ...

. 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 ( phaneritic) 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 cools and solidifies und ...

. 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 Eon ( , also spelled Archaean or Archæan) is the second of four eon (geology), geologic eons of History of Earth, Earth's history, representing the time from . The Archean was preceded by the Hadean Eon and followed by the Proterozo ...

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 ( ) is a clay mineral, with the chemical composition Al2 Si2 O5( OH)4. It is an important industrial mineral. It is a layered silicate mineral, with one tetrahedral sheet of silica () linked through oxygen atoms to one octahed ...

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