Mount Weld is a mountain and a mine site in Western Australia

Western Australia

Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...

, located about 30 km south of Laverton and 120 km east of Leonora

Leonora, Western Australia

Leonora is a town in the Goldfields-Esperance region of Western Australia, located northeast of the state capital, Perth, and north of the city of Kalgoorlie. At the 2006 census, Leonora had a population of 401, about a third of whom are of Aboriginal descent. The area is extremely arid, with a...

. It ranks as one of the richest major rare earth

Rare earth element

As defined by IUPAC, rare earth elements or rare earth metals are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium...

 deposits in the world.

Rare earths are contained in secondary phosphates and aluminophosphates, presumably derived from weathering of the Proterozoic Mount Weld carbonatite

Carbonatite

Carbonatites are intrusive or extrusive igneous rocks defined by mineralogic composition consisting of greater than 50 percent carbonate minerals. Carbonatites may be confused with marble, and may require geochemical verification....

  The primary commercial interest at the site is targeted towards oxides as well as further niobium

Niobium

Niobium or columbium , is a chemical element with the symbol Nb and atomic number 41. It's a soft, grey, ductile transition metal, which is often found in the pyrochlore mineral, the main commercial source for niobium, and columbite...

 and tantalum

Tantalum

Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as tantalium, the name comes from Tantalus, a character in Greek mythology. Tantalum is a rare, hard, blue-gray, lustrous transition metal that is highly corrosion resistant. It is part of the refractory...

 deposits within the intrusive pipe of the Mount Weld carbonatite, which is approximately three kilometers in diameter.

The main deposits are hosted within the soil/regolith horizon that blankets the entire carbonatite and form shallow lenses within 60 m of the surface. The most important rare earth oxide deposit, the Central Lanthanide Deposit, CLD, is located at the center of the carbonatite with the niobium/tantalum and other deposits generally located towards outer fringes. Discovered in 1988, the CLD represents a spectacular enrichment of rare earth deposit sediments. The deposit is believed to be the largest and highest grade of its type in the world.

The Mount Weld deposit is owned by ASX-listed Lynas Corporation, which raised A$450 million equity from J. P. Morgan

J. P. Morgan

John Pierpont Morgan was an American financier, banker and art collector who dominated corporate finance and industrial consolidation during his time. In 1892 Morgan arranged the merger of Edison General Electric and Thomson-Houston Electric Company to form General Electric...

 in 2009 to fund the development of a mine and also a processing plant in Kuantan

Kuantan

Kuantan is the state capital of Pahang, the 3rd largest state in Malaysia. It is situated near the mouth of the Kuantan River and faces the South China Sea. If one measures the distance along the east coast of Peninsular Malaysia, it is located roughly halfway between Singapore and Kota Bharu...

, Malaysia. Once operational, the Mount Weld mine is expected to be the largest source of rare earth elements outside of China.