Alunite
The mineral alunite Kal3(SO4)2(OH)6 has a colour ranging from yellow grey to white. It is a hydrated aluminium potassium sulphate therefore a source of both potash and alum.
The mineral alunite, or alumstone, is rare in Australia, a country short on potash, therefore all of its current potash requirements are imported. Alunite is usually located in volcanic rocks that are rich in potassium having been formed with a sulphuric acid solution coming into contact with rock during oxidation and leaching of metal sulphide deposits. It is also located in what are known as fumaroles (deep openings in the ground usually in the vicinity of volcanoes).
The Formation of Alunite is Called Alunitisation
When alunite is formed as a result of sulphuric acid acting on potassium rich feldspar it is called 'alunitisation.' The sulphuric acids are accompanied by hydrothermal solutions that are usually rich in certain metals. These solutions cause alunite to become a rock forming mineral when large deposits of the mineral result. Many of these rock formations can easily be mistaken for calcite (limestone) or dolomite rocks. An acid test can determine the difference as alunite does not bubble as do other formations.
Alunite is primarily Mined for the Production of Potash and Alum
On first appearance alunite looks much like fine grained limestone, magnesite, dolomite or even anhydrite. The more compacted examples found in Hungary are that tough and hard they were used as millstones. It is often mined for the purposes of producing aluminium and potash. When sodium replaces potassium, particularly when the sodium content is high it is known as natroalunite. It is not soluble in weak acids or water but is readily soluble in sulphuric acid. Jarosite is a form of alanite where the aluminum is replaced by iron. This occurs on iron sulphate ores as a secondary mineral.
Australia has Historically Mined Alunite
There has been some historical production of potash in Australia, these have included the following:
Australian Mines that produce Bauxite
Gove (NT)
Up to 600 workers employed at the Gove bauxite refinery in the Northern Territory face an uncertain future as Pacific Aluminium suspends alumina production.
Ely (QLD)
The Ely Alcan Queensland Pty Ltd agreement at the Weipa bauxite mine is due to expire in 2041 but an option will give it a further 21 years extension.
Skardon River (QLD)
Gulf Alumina acquired 100 percent of the Skardon River tenement in 2011 from its koalin mining joint partner to develop the mining of bauxite at the site
Weipa (QLD)
The Weipa bauxite mine on the western side of the Cape York Peninsula in northern Queensland is both owned and operated by Rio Tinto Alcan.
Huntly (WA)
The Huntly mine in Western Australia is the largest bauxite mine in the world currently producing about 23 million tonnes of bauxite annually.
Willowdale (WA)
The Willowdale bauxite mine that commenced production in 1984 still processes 10 million tonnes of bauxite a year at the nearby Wagerup Refinery.
Worsley (WA)
The Worsley bauxite mine and alumina refinery in South West Western Australia employs more than 1,800 people and produces 4.6 million tonnes of alumina annually.
South Aurukun (QLD)
The South Aurukun bauxite tenements on the Cape York Peninsula in Far North Queensland are held by Gulf Alumina.
Marchinbar Island (NSW)
The Marchinbar Island bauxite deposit in far north Northern Territory could be mined to satisfy a growing demand from China in the near future.
Kwinana Refinery (WA)
The Kwinana refinery in WA employs around 1,000 direct employees with 60 percent living in the nearby towns of Rockingham, Cockburn and Kwinana.
Wagerup Refinery (WA)
The Alcoa owned Wagerup alumina refinery in W.A. has received governmental approval to lift alumina production from 2.6 to 2.65 million tonnes annually.
Pinjarra Alumina Refinery (WA)
The Pinjarra alumina refinery, near Mandurah south of Perth, is an important part of Alcoa's three refinery system in Western Australia.
Portland Aluminium Smelter (VIC)
The Portland Aluminium smelter in western Victoria, a joint venture operation between Alcoa, CITIC and Marubeni, caters solely to the Asian market.
Felicitas (WA)
The Felicitas bauxite project in Western Australia contains a bauxite resource of 220 million tonnes that will give it a life of mine of 25 years
South Of Embley (QLD)
Despite Rio Tinto placing its South of Embley bauxite project in Cape York, Queensland, on hold for 18 months it still considers it a 'good project.'
Bauxite Hills (QLD)
The Bauxite Hills Project on the Cape York Peninsula in Queensland is hoping to take advantage of an expected increase in the demand for Alumina.
Bald Hill (TAS)
Australian Bauxite Limited's Bald Hill mine, in Tasmania, is to start production in December, 2014. It is the first new bauxite mine in Australia, for over 35 years.
Urquhart Point (QLD)
The Urquhart Point Heavy Mineral Sands Project in Cape York in Far North Queensland is expected to begin production in mid-2015.
Amrun (QLD)
The Amrun bauxite project in far north Queensland, that was previously known as the 'South of Embley' project has been approved for development and expected to be in production by 2019.
