Bali Lo (Casleys; Anticline prospect), Ashburton Downs Station, Ashburton Shire, Western Australia, Australia

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Longitude 23,24S, 116,55E.

The Bali Lo Prospect is found in rough, remote mountainous desert country, about 11 kilometres south-west of the Ashburton Downs homestead, in the southern portions of the Capricorn Range. The track to it is far longer, rocky and difficult. It has been little visited due to its remoteness, yet specimens from the location have been available , despite the few photographs on Mindat. Of particular note is the large number of species found at the location.

To a lesser degree specimens have also been seen from Bali Hi, 1 kilometre east of Bali Lo, and Mineral Claim 84. Bali East is about 2 kilometres east, Stockyard Gully 3 kms south and Bali South 3 kilometres south-east, all from Bali Hi. The Ledge deposit is 3 kilometres west of Bali Lo. Little in the way of specimens have been seen from these last four locations so far, although the Western Australian Museum holds many specimens.

The Bali Lo prospect is little more than part of a ridge bulldozed over a few square metres, yet has been a rich source of specimens.

Ashburton Mining, Westfield Mining, Picklands Mather, and Barrick Mines have all explored the area. The only mining to take place was between 1963-1966, of 129 tonnes of secondary copper material grading 8.8% copper.

The Bali Lo area is associated with well known geologist Blair Gartrell, who collected several thousand specimens between 1985-1990. The new species ashburtonite (Mineral Claim 84) and gartrellite were discovered by him from these deposits. While likely from Mineral Claim 84 or Bali Lo,the exact location for gartrellite needs clarification, as all sources found simply state Ashburton Downs.

The country rock in the area is slate, siltstone, conglomerate, greywacke, and tuff of the Ashburton Formation. Overlying this is shelf-facies conglomerate, dolomite, greywacke, and minor tuff of the Capricorn Formation, all folded into a major west north-west anticline.

Bali Lo is located close to the hinge of the anticline on the Bali Shear fault zone, near the contact with the above two rock formations. The intensely decomposed deposits in the area hold secondary copper species hosted by quartz veins, with small pods of limonite with disseminated malachite, azurite, chrysocolla, and copper arsenates. Primary sulphide minerals include arsenopyrite, pyrite, marcasite, galena, tennantite and chalcopyrite. The primary mineralisation is dominated by sulphides and arsenides of lead, iron, copper and zinc.

The locations are of interest due to the open cellular boxwork from the decomposition of tennantite. This creates cells often containing a number of mainly arsenate species. Various species though are also found outside of this framework.

The tennantite has been intruded by veinlets of various Cu, Fe and Pb arsenates dissolving along fractures, creating an acid environment and new species.

The veinlets have been found to contain olivenite and chenevixite as major components; and more minor reddish-brown mawbyite, gartrellite, mimetite, bright green arsentsumebite, and green bayldonite.

Species found lining the cells are olivenite as olive-green to brown elongated crystals and fine grained yellowish-white masses; chenevixite as porous yellowish-green masses; nodular and arborescent forms of mawbyite; yellow to brownish or yellow or greenish-yellow gartrellite; arsentsumebite; rare clusters of pseudo-cubic crystals from the alunite supergroup minerals; tiny red crystals of cinnabar; rare bluish-green prismatic and pyramidal crystals of brochantite; hematite and goethite as red and brown wall coatings; occasional blue grains of chrysocolla; and possibly perroudite.

Mineral List

Adamite Aheylite Alunite Arsenogorceixite Arsenopyrite Arsentsumebite Atacamite Azurite Baryte Bayldonite Beaverite-(Cu) Beudantite Brochantite Caledonite Ceruleite

Chalcocite Chalcophanite Chalcopyrite Chenevixite Chrysocolla Cinnabar Clinoclase Corkite Cornubite Cornwallite Coronadite Duftite Galena Gartrellite Goethite

Groutite Hematite Hidalgoite Hydrozincite Kaolinite Lavendulan Libethenite Limonite Luetheite Malachite Marcasite Mawbyite Metatorbernite Metazeunerite Mimetite

Olivenite Osarizawaite Paratacamite Perroudite Philipsbornite Pseudomalachite Pyrite Pyrolusite Scorodite Tennantite Tetrahedrite Tripuhyite

57 entries listed. 56 valid minerals.

References