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Tosca Mine (Tosca's Hope), Ammaroo Station (Amaroo Station), Sandover, Barkly Region, Northern Territory, Australia

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Latitude & Longitude (WGS84): 21° 30' 11'' South , 135° 25' 36'' East
Latitude & Longitude (decimal): -21.5033333333, 135.426944444


A Turquoise mine.

Turquoise is quite rare in Australia. This mine is the only known commercial production of the gemstone in Australia. It was examined in detail in the early 1970's, with several pits bulldozed to expose the layer of turquoise, finding carving and specimen grade material, but only minor trace gem grade turquoise was found. Specimens have been regularly seen for sale, but from what period is not known. The area is covered by an aboriginal sacred site order, which may have limited commercial mining, and exploration.

The mine is about 30 kilometres north of the Ammaroo pastoral station homestead, and nearby Ampilatwatja indigenous community. A road heads north of here from the Sandover Highway towards the Elkedra Station. About 5 kilometres past the turn-off to the Murray Downs Station, a minor track heads east, quickly coming to a dam and several waterholes. The track continues in a generally easterly direction for about 5 kilometres to a collection of shallow pits. Minor pits can be seen to the north in low hills.

Turquoise layers are found within claystone, overlying a conglomerate bed. Under this is quartzitic sandstone, grading in places into purplish phyllite that is a metamorphosed sandy shale to siltstone. The basal part of the claystone contains abundant kaolin coloured khaki, rust and browns. The turquoise bed is half an inch to 6 inches thick. Trace malachite and chrysocolla has been found with the turquoise.

Specimens have to be waxed as they also contain montmorillonite, a clay which expands when in contact with water. Wavellite is noted at the deposit as radio active phosphate layers, while limonite stains are common. Dehydrated variscite is noted by O'Toole in green, blue, yellow or white colours.

Explored by VAM limited 1968-1971, or M.E. Morrison, International Turquoise Pty Ltd 1972-1977, and Shaft and Tunnel Pty Ltd 1994-1995.

A nearby deposit (possibly to the north) is called Cumton No. 1, where turquoise is found with malachite. The turquoise layer is under a ferriginous gossanous like cap, and immediately on top of quartzitic conglomerate. The turquoise is a 2 to 3 inch layer, said to be poor quality being leached and weathered, with a patchy distribution.



Mineral List


10 valid minerals.

Rock Types Recorded

Entries shown in red are rocks recorded for this region.

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The above list contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.

References

O'Toole, A. (1973) Evaluation of the Ammaroo Turquois Deposit, International Geological Consultants Australia Pty Ltd.

Hosking, A. J. (1995) EL 8607 Tosca, First annual-final report - for year ending 15/6/1995. Shaft and Tunnel Pty Ltd Report Number: ST/8607/1.

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