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Coocoran Opal Fields, Lightning Ridge, Finch Co., New South Wales, Australiai
Regional Level Types
Coocoran Opal Fields- not defined -
Lightning RidgeRidge
Finch Co.County
New South WalesState
AustraliaCountry

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Latitude & Longitude (WGS84): 29° 27' 48'' South , 147° 45' 39'' East
Latitude & Longitude (decimal): -29.46333,147.76083
GeoHash:G#: r6c06kk5s
Köppen climate type:BSh : Hot semi-arid (steppe) climate
Nearest Settlements:
PlacePopulationDistance
Lightning Ridge2,685 (2012)21.5km
Cumborah493 (2013)31.5km
Goodooga330 (2012)49.1km


The Coocoran opal fields consist of about 50 named opal fields are located about 21 kilometres east of the town of Lightning Ridge. A "field" is an area where opal mineralisation has been found. Locally an opal field is known as a "rush" and is often named after the opal miner that initially found mineralisation in that area.

On the Coocoran opal fields a rush can range in area from about 1 hectare up to more than 20 hectares. Peak production occurred in the period from late 1980s to late 1990s.

Underground and open cut mining techniques are used to extract opal from depths ranging from near surface up to 25 metres underground. The host rock is the Cretaceous Griman Creek Formation which is predominantly composed of freshwater (rarely estuarine?) claystones and sandstones.

Most gem opal from the Coocoran opal fields is found as "nobby" opal. Nobby opal occurs as spheroidal or disc like pieces of opal that range from about 1 to 15cm in diameter sporadically distributed through claystone layers.

Opalised fossils also occur sporadically. Fossils include bivalve shells, gastropod shells, dinosaur bones & teeth, turtle shell & bones, crustacean gastroliths, plant stems & fruiting bodies, plesiosaur bones & teeth, monotreme bones, etc.

Regions containing this locality

Australian Plate (Australia Plate)Tectonic Plate
Eromanga Basin, AustraliaBasin
Lachlan Orogen, AustraliaOrogen
Eastern Province, Lachlan Orogen, AustraliaGeologic Province

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Mineral List

Mineral list contains entries from the region specified including sub-localities

1 valid mineral.

Detailed Mineral List:

Opal
Formula: SiO2 · nH2O
Localities: Reported from at least 26 localities in this region.
Reference: Cram, L. (2004): A Journey with Colour, Vol 2, Part B - A History of Lightning Ridge Opal 1873-2003, Len Cram.
Opal var: Black Opal
Formula: SiO2 · nH2O
Localities: Reported from at least 16 localities in this region.
Reference: Cram, L. (2004): A Journey with Colour, Vol 2, Part B - A History of Lightning Ridge Opal 1873-2003
Opal var: Bone Opal
Formula: SiO2 · nH2O
Localities: Reported from at least 8 localities in this region.
Reference: Cram, L. (2004): A Journey with Colour, Vol 2, Part B - A History of Lightning Ridge Opal 1873-2003
Opal var: Harlequin Opal
Reference: Cram, L. (2004): A Journey with Colour, Vol 2, Part B - A History of Lightning Ridge Opal 1873-2003
Opal var: Honey Opal
Formula: SiO2 · nH2O
Reference: Cram, L. (2004): A Journey with Colour, Vol 2, Part B - A History of Lightning Ridge Opal 1873-2003
Opal var: Precious Opal
Formula: SiO2 · nH2O
Localities: Reported from at least 15 localities in this region.
Reference: - Smith, E. & R. (1999): Black Opal Fossils of Lightning Ridge - Treasures from the Rainbow Billabong, Kangaroo Press, East Roseville. - Cram, L. (2004): A Journey with Colour, Vol 2, Part B - A History of Lightning Ridge Opal 1873-2003, Len Cram. - Australian Opal Centre web site http://www.australianopalcentre.com/
Opal var: Shell Opal
Habit: Amorphous
Colour: Transparent to opaque, 'amber', white, grey and black opal sometimes showing colour play which varies widley in colour, pattern and brightness
Description: Opal has typically replaced the shell of articulated freshwater bivalves, although in some cases the interior of the shell is also replaced with opal. In some cases the opal is all gem quality.
Reference: - Smith, E. & R. (1999): Black Opal Fossils of Lightning Ridge - Treasures from the Rainbow Billabong, Kangaroo Press, East Roseville.
Opal var: Wood Opal
Formula: SiO2 · nH2O
Localities: Reported from at least 12 localities in this region.
Reference: - Smith, E. & R. (1999): Black Opal Fossils of Lightning Ridge - Treasures from the Rainbow Billabong, Kangaroo Press, East Roseville.

List of minerals arranged by Strunz 10th Edition classification

Group 4 - Oxides and Hydroxides
Opal4.DA.10SiO2 · nH2O
var: Black Opal4.DA.10SiO2 · nH2O
var: Bone Opal4.DA.10SiO2 · nH2O
var: Harlequin Opal4.DA.10SiO2 · nH2O
var: Honey Opal4.DA.10SiO2 · nH2O
var: Precious Opal4.DA.10SiO2 · nH2O
var: Shell Opal4.DA.10SiO2 · nH2O
var: Wood Opal4.DA.10SiO2 · nH2O

List of minerals arranged by Dana 8th Edition classification

Group 75 - TECTOSILICATES Si Tetrahedral Frameworks
Si Tetrahedral Frameworks - SiO2 with H2O and organics
Opal75.2.1.1SiO2 · nH2O
Unclassified Minerals, Mixtures, etc.
var: Black Opal-SiO2 · nH2O
var: Bone Opal-SiO2 · nH2O
var: Harlequin Opal-SiO2 · nH2O
var: Honey Opal-SiO2 · nH2O
var: Precious Opal-SiO2 · nH2O
var: Shell Opal-SiO2 · nH2O
var: Wood Opal-SiO2 · nH2O

List of minerals for each chemical element

HHydrogen
H OpalSiO2 · nH2O
H Opal (var: Precious Opal)SiO2 · nH2O
H Opal (var: Wood Opal)SiO2 · nH2O
H Opal (var: Black Opal)SiO2 · nH2O
H Opal (var: Honey Opal)SiO2 · nH2O
H Opal (var: Bone Opal)SiO2 · nH2O
OOxygen
O OpalSiO2 · nH2O
O Opal (var: Precious Opal)SiO2 · nH2O
O Opal (var: Wood Opal)SiO2 · nH2O
O Opal (var: Black Opal)SiO2 · nH2O
O Opal (var: Honey Opal)SiO2 · nH2O
O Opal (var: Bone Opal)SiO2 · nH2O
SiSilicon
Si OpalSiO2 · nH2O
Si Opal (var: Precious Opal)SiO2 · nH2O
Si Opal (var: Wood Opal)SiO2 · nH2O
Si Opal (var: Black Opal)SiO2 · nH2O
Si Opal (var: Honey Opal)SiO2 · nH2O
Si Opal (var: Bone Opal)SiO2 · nH2O

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Cenozoic
0 - 66 Ma



ID: 871117
sedimentary rocks 72357

Age: Cenozoic (0 - 66 Ma)

Description: Undifferentiated consolidated Cenozoic sedimentary rocks; sandstone, limestone, conglomerate, siltstone, duricrust; commonly ferruginised or silicified; may be poorly consolidated, highly weathered, and dissected by present day drainage.

Comments: sedimentary siliciclastic; regolith; synthesis of multiple published descriptions

Lithology: Sedimentary siliciclastic; regolith

Reference: Raymond, O.L., Liu, S., Gallagher, R., Zhang, W., Highet, L.M. Surface Geology of Australia 1:1 million scale dataset 2012 edition. Commonwealth of Australia (Geoscience Australia). [5]

Tertiary
2.588 - 66 Ma



ID: 3187964
Cenozoic sedimentary rocks

Age: Cenozoic (2.588 - 66 Ma)

Comments: Great Artesian Basin

Lithology: Laterite,clay,gravel,sand,silt

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License

References

Sort by

Year (asc) Year (desc) Author (A-Z) Author (Z-A)
Aracic, Stephen (1999), Rediscover Opals in Australia, published 1999 by the Kingswood Press.
Smith, E. & R. (1999): Black Opal Fossils of Lightning Ridge - Treasures from the Rainbow Billabong, Kangaroo Press, East Roseville.
Cram, L. (2004): A Journey with Colour, Vol 2, Part B - A History of Lightning Ridge Opal 1873-2003, Len Cram.

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