Staurolite
Staurolite is an iron/aluminium silicate produced commercially as a by-product from mineral sands placer deposits. Its crystals are usually dark brown.
Staurolite ( iron aluminium silicate hydroxide) is a hard mineral, quite brittle and characterised by its dull lustre. It is usually of a dark brown colour and sought after by gem stone fossickers because of its propensity to display cruciform patterns known as 'fairy crosses.' Its name is derived from the Greek word for cross, 'stauros.' Facts on the mineral staurolite include the following:
Staurolite is produced on a commercial scale as a by product from heavy mineral sands placer deposits.
These are usually found in beach sand environments due to the concentration of specific gravity of mineral grains. It is often associated with the production of zircon and titanium. Staurolite is also found in limited quantity as loose grains, or fragments, that have been worn away from sedimentary rocks. Although the presence of staurolite can be widespread, it remains a rare mineral and only mined in few places around the world, namely the USA, Australia, Ukraine, India and Russia.
Staurolite, being a metamorphic mineral, is found useful by geologists in determining the degree of metamorphism that has taken place.
Metamorphism being the change in rock structure as a result of undergoing exposure to intense pressure, heat and various chemicals over long periods of time. Its famous twinned crystals that form the shape of a cross is a classic penetration twin where it appears as if two crystals grew into and out of each other. In fact it forms two twin types. One at about 90 degrees and one at close to 60 degrees. The 90 degree twin is the most sought after although the 60 degree twin is more common.
The hardness of staurolite is what makes it commercially attractive.
It has a resistance to weathering and chemical attacks, a high melting point, low thermal expansion and moderate specific gravity. For these reasons it is used in the following ways:
- As an abrasive in sandblasting operations and as foundry sand
- For the etching and cutting of monumental stone
- Its use in paint primers as a filler material known as staurolite flour
- In cement production as a source of alumina
When used for sandblasting it is applied to a metal surface with the use of compressed air through a nozzle.
When applied in this way the grains of staurolite cut through and remove and residual coatings on the surface of the metal such as rust or paint. Once cleaned in this manner the surface is once again ready for painting or welding.
Staurolite can also be made cut through metal with it being applied by means of a water jet.
The mineral is sprayed in a fine jet of water at a very high pressure. The edge of the cut is smooth and the cutting action carried out with the use of a robotic arm that makes it suitable for cutting out patterns or templates. This means it is the most suitable way of cutting intricate shapes be it on sheets of glass, stone, plastic and metal.
The only source of commercial staurolite in Australia is at the Cooljarloo mineral sands placer deposit near Perth in Western Australia that primarily mines titanium. Western Australian sourced staurolite is separated from the other heavy minerals in concentrate form in the Chandala dry mill. Staurolite is not looked on as a mineral having potential growth because of industry demand, as production world wide is considerably constrained because of its limited availability.
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.
