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Opal Lexicon

Australian Opal Fields

Australia is the world's largest and most important producer of opal. Around 95 % of the world's production come out of Australian opal fields. Australian opals are usually of sedimentary origin and considered particularly stable. There are also some opal mining fields in Australia that produce opal of volcanic origin (e.g. Tintenbar, NSW). However these are only of interest for collectors but of no importance for the jewelry sector. Some of the most important and famous mining fields are displayed on the opal origin map below:
 

Lambina Mintabie Coober Pedy Andamooka White Cliffs Lightning Ridge Queensland Opal Fields Australian Opal Mining Fields


Today the opal production has decreased compared to its heyday due to increased fuel costs, restrictions on the use of explosives and an antiquated mining law. In addition many of the old opal mining fields are already well mined not to say mined out and the prospecting for new opal fields is an expensive work. Therefore only a few full-time miners are left and concentrated around the most important localities like Lightning Ridge, Coober Pedy, Mintabie, Lambina and Queensland.

 

  Coober Pedy opal fields

Danger signs and uncountable hummocks from underground
mining are bordering the Stuart Highway around Coober Pedy

The opal mining field of Coober Pedy lies at the Stuart Highway, 750 km north of Adelaide. A 14-year old boy who was camping with his father's gold prospecting party discovered opal in 1915 as well as a waterhole that saved their lives.
The name Coober Pedy was derived from the Aboriginal kupa piti meaning "white man in a hole" (or "boy's waterhole" if you read some other texts). The population is around 2500. Due to unbearable summer temperatures which may exceed 50C most people are living underground in so called "dugouts".
Mining is usually done by underground tunneling. The opal dirt (mullock) is conveyed to the surface by blowers or automatic bucket tippers.
Most opal found is Light Opal and Crystal Opal. However  there is also some Dark Opal and very little Black Opal. While most of Coober Pedy opal is seam opal, there is also a significant part found in the form of opalized fossils (e.g. shells, snails, belemnites, bones, teeth and wood).
The mining works extend over an area 50 km long, running approximately parallel to the Stuart Highway from north to south. Opal is found in deeply weathered white to mauve Bulldog Shale of cretaceous age. Within the light, porous host rock (sandstone), opal may be found as veins in horizontal "levels" or in steeply dipping "verticals" down to 25 m below the surface. Distribution is unpredictable and opal may not persist from one claim to the next.
From 1978 to 1990 Coober Pedy produced approximately 20 - 30 million worth of rough opal annually. In 2002 Coober Pedy's production has fallen to 25% of its heyday. Today only a limited number of full-time miners is left.

 

  Lightning Ridge opal mining field - Lunatic Hill

Lunatic Hill, a huge open-cut at Lightning Ridge

This is the home of the world famous Black Opal. Lightning Ridge is located almost 600 km north of Sydney. First finds of opal around this area date back to 1873. However it wasn't until 1903 that Charlie Nettleton and Jack Murray sold their first parcel of Black Opal to E. F. Murphy, an assistant of the famous Tullie Wollaston who was the main power behind introducing Australian Opal to the world's market.
Lightning Ridge got its name probably due to a terrifying electrical storm that killed a shepherd, his dog and 600 sheep whilst sheltering on one of the ridges.
The population is around 3000. However this may quickly change by new discoveries or a large find which may produce a new rush. So happened in the late 1980s when the Coocoran field 30 km to the west of the township produced stunning Black Opal in great quantities. Mining is usually done by underground tunneling. Very rich ground may also be worked by an open-cut like the famous Lunatic Hill since it pays to work the entire area completely and enables to remove and process all opal dirt. With underground mining you will always have to leave walls and pillars of host rock to prevent a cave-in.
Most opal found is Dark (Semi-black), Black and Crystal Opal as well as some Light Opal and a few opalized fossils. Opal around Lightning Ridge is usually found in the form of nodules called "nobbies". This form is considered to produce the world's highest quality of opal. Farther outlying fields like Grawin, Glengarry, Sheep Yards, and Mulga Rush predominantly produce Dark and Black Seam Opal.
Today top-quality Black Opal (brilliant red on black) are the most valuable of all opals and can fetch record prices sometimes at more per carat than good quality diamond. Particularly since there is by far not enough quality Black Opal to satisfy world demand.

 

  Mintabie opal field - open cut mining

Open-cut mining at Mintabie with a huge 100 tons excavator

Mintabie, population around 200, is situated 35 km west of Marla off the Stuart Highway (or about 350 km northwest of Coober Pedy). Apart from Lightning Ridge it is the only important source of Black Opal.
Although opal miners discovered the field in the 1920s, it was only in the 1980s that production increased to make it a commercial field.
At the end of 1976 miners moved in with bulldozers and heavy mining equipment which was needed to rip the hard sandstone.
During the 1980s Mintabie was the largest producer of precious opal in Australia and over 500 miners lived and worked on the field. Fortunes were made in open-cuts at Old Field. The peak in production was reached at 1988 and drastically declined in the following years. Up to 100 large bulldozers and many scrapers and excavators quickly mined out this very rich area. Today only a small number of full-time miners is left.
Most mining is done by open-cut mining as well as some underground tunneling. The opal found comprises Light, Dark, Black and Crystal Seam Opal. Mintabie opal is extraordinary hard, sometimes even hard enough to scratch agate. Host rock is a kaolinitic sandstone of probable Ordovician age. The opal is found as seams in horizontal or arcuate levels or infillings of steeply dipping verticals down to depths of 25 m.
Some people say that during the first 5 years of mining Mintabie produced more opal than Coober Pedy has to this date.

 

  Lambina opal mining field - prospect drilling

Prospect drilling at Lambina

Andamooka
Andamooka is located in the harsh desert, 520 km north of Adelaide, near the western shore of Lake Torrens. It is reached travelling by sealed road 30 km east from Roxby Downs which today employs much of Andamooka's population in their uranium mines.
Opal was discovered in 1930 and until 1972 Andamooka was a major producer of precious opal. It was famous for producing top-quality Crystal Opal which may occur in the form of seams and so called "blobs" (similar to nobbies but with sizes up to a small loaf). Additionally Matrix Opal and "Painted Ladies" (thin films of opal in joints of quartzite boulders which are split open parallel to the film of opal) come from Andamooka. Today this field is worked out with very little commercial production since the 1970s.

Lambina
Located 58 km northeast of Marla. First workings probably date from the 1930s. This field has steadily grown when a scheme of arrangement was agreed with the farming landholder. In 2002 around 300 miners were working open-cuts with bulldozers and excavators.
Opal is found in the form of Light and Dark Seam Opal as well as some Crystal and very little Black Opal. However rough material often has a distinct appearance from classical seam opal forming as disjointed chunks coated with dirt on all sides why it was sometimes incorrectly termed alluvial opal. Today there are not so many miners left.

Queensland fields
The fields are spread across 1000 km, covering a large part of the entire state Queensland. They produce almost all the world's supply of Boulder Opal. Some of the most important locations are Yowah, Quilpie, Koroit, Jundah, Opalton and Eromanga. Mining is mostly done by open-cut mining.
Boulder Opal usually is an ironstone rock with thin veins of opal that are too thin to be cut without retaining a backing of ironstone. Therefore the boulders are split open or sawn parallel to the vein of opal sometimes producing a matching pair of opals. It may also happen that the vein of opal is thick enough to be cut into solid opals. Apart from Boulder Opal there are also large quantities of Boulder Matrix Opal found (many fine veins and small patches of opal surrounded by host rock).

White Cliffs
White Cliffs lies in New South Wales and is situated 200 km northeast of Broken Hill. The field was discovered by kangaroo shooters in 1889. Commercial mining commenced in 1890. The town quickly developed and within 9 years there were 4500 miners on the field. The production declined from 1902 to 1915 and a big exodus of miners to the opal fields of Lightning Ridge reduced the number of miners to 100 by 1919. The main run was worked out by 1930.
For many years White Cliffs produced the first commercially accepted opal and excited the world's market since this opal far surpassed opal mined in Hungary. Beside the famous "Pineapples" (pseudomorphs of opal after glauberite crystal aggregates) White Cliffs produced fine quality seam opal and opalized fossils (shells, wood, bones).

 

  • Worldwide opal deposits

  Ethiopian opal (thunder-egg)

Split nodule of Ethiopian opal (thunder-egg)

Apart from Australia opal occurs at many other localities around the world. For example in Brazil, Mexico, Peru, Honduras, Guatemala, Nicaragua, Grand Canary, USA, Canada, Ethiopia, Zimbabwe, South Africa, Nigeria, Somalia, Mali, Germany, Czech Republic, Turkey, Kazakhstan, Indonesia and New Zealand.
However only a few of these areas are of limited commercial importance since around 95 % of the world's production of opal come out of Australia.

 


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