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The Koroit opal field is an 
opal
Opal is a hydrated amorphous form of silica (SiO2ยท''n''H2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Due to its amorphous property, it is classified as a mineraloid, unlike crystalline form ...
mining area in Paroo Shire in South West Queensland
South West Queensland is a remote region in the Australian state of Queensland which covers . The region lies to the south of Central West Queensland and west of the Darling Downs and includes the Maranoa district and parts of the Channel Coun ...
, Australia. It is located about 80 km north northwest of Cunnamulla. It is not a town, nor should it be confused with the town of Koroit
Koroit is a small rural town in western Victoria, Australia a few kilometres north of the Princes Highway, north-west of Warrnambool and west of Melbourne. It is in the Shire of Moyne local government area located amidst rolling green past ...
in rural western Victoria
Victoria most commonly refers to:
* Victoria (Australia), a state of the Commonwealth of Australia
* Victoria, British Columbia, provincial capital of British Columbia, Canada
* Victoria (mythology), Roman goddess of Victory
* Victoria, Seychelle ...
, Australia. It has neither electricity nor running water. Koroit is close to the town of Yowah which also produces a similar type of opal.
The Koroit opal field is known for the very distinctive type of boulder opal that is found in its mines. In Queensland boulder opal is found within a 300 km wide belt of sedimentary rocks in the Winton Formation
The Winton Formation is a Cretaceous geological formation in central-western Queensland, Australia. It is late Albian to early Turonian in age. The formation blankets large areas of central-western Queensland. It consists of sedimentary rocks suc ...
. Here opal is found as a kernel in small concretion
A concretion is a hard, compact mass of matter formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular ...
s.
The Koroit Opal field was discovered in 1897 by Lawrence Rostron. The most recent mining events started in 1972 when the popularity and profitability of the stone increased. The mining is done by either open cut large scale mining or by underground shafts.
See also
*Mining in Australia
Mining in Australia has long been a significant primary sector industry and contributor to the Australian economy by providing export income, royalty payments and employment. Historically, mining booms have also encouraged population growth ...
References
Mining in Queensland Geology of Queensland South West Queensland Gemstone mines {{Australia-geology-stub