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Ilmars prospect, Alice Downs Station, Halls Creek Shire, Western Australia, Australia

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Latitude & Longitude (WGS84): 18° 3' 58'' South , 127° 51' 46'' East
Latitude & Longitude (decimal): -18.06606,127.86270
GeoHash:G#: qufcjx4v8
Locality type:Prospect
Köppen climate type:BSh : Hot semi-arid (steppe) climate

Located in the northern Ilmars Range, about 30 kilometres north north-east of Halls Creek, and 5 kilometres east of the Great Northern Highway. Described as 200 yards from the road to Saunders Creek, on the crest of a sharp ridge 50 feet high. Much explored, with mineralisation found, but nothing yet economic. Cu-Pb-Zn prospect. First explored by Peko Mines NL in 1963.

The deposit occurs is schists, variably quartz-sericite, quartz-chlorite, carbonate rich, and graphite schists, with interbedded tuff, limestone, calcareous mudstone, shale and chert. Oxidation reaches 18 to 30 metres below the surface.

Mineralisation occurs for 1800 metres long, with lower grades another 3000 metres further south. Pyrite and/or pyrrhotite dominates, with sphalerite, and minor galena, chalcopyrite, trace arsenopyrite and tetrahedrite-tennantite. The sulphides range from fine grain disseminations to semi massive concentrations. Most of the mineralisation is in quartz and feldspathic schist.

The prospect was discovered with exposed surface gossans in 1963. These are orange or red/brown soft porous limonitic rocks, commonly showing boxwork, with malachite, cuprite, hydrozincite, minor azurite, chalcocite, covellite, native copper, and rare smithsonite and cerussite. The gossan was found in two sections, of thinly bedded dolomitic shale separated by a barren zone. The gossans strike north for 850 feet, average 60 feet wide, dips 65 degrees west. They are split by a leached zone 15 feet wide of unmineralised tremolite. The secondary copper minerals are abundant as bands, patches, and small lenses.

Mineral List

25 valid minerals.

Rock Types Recorded

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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.

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1600 - 2500 Ma

ID: 3186269
Paleoproterozoic sedimentary rocks

Age: Proterozoic (1600 - 2500 Ma)

Comments: Arunta Block

Lithology: Sedimentary rocks

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]

1800 - 2050 Ma

ID: 773047
Biscay Formation

Age: Orosirian (1800 - 2050 Ma)

Stratigraphic Name: Biscay Formation

Description: Low to medium grade metamorphosed basaltic volcanics, volcaniclastics, dolerites, pelites and carbonates; carbonate and chert lenses, and local sandstone interbeds

Comments: igneous mafic volcanic; igneous volcanic; synthesis of multiple published descriptions

Lithology: Igneous mafic volcanic; igneous volcanic

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]

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

This page contains all mineral locality references listed on 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 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.


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Butt, C.R.M., Smith, R.E. (1980), Conceptual Models in Exploration Geochemistry, Developments in Economic Geology 13, The Association of Exploration Geochemists, Special Publication No. 8, Journal of Geochemical Exploration, Vol 12 2/3, 1980 (section in book by R. Halligan Perth Consultant and J.L. Harris from Amoco Minerals Australia Co.).
Dow, D.B., Gemuts, I. (1969), Geology of the Kimberley Region Western Australia: The East Kimberley, Department of National Development/ Bureau of Mineral Resources Geology and Geophysics/ Geological Survey of Western Australia, Bulletin 106, 1969

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