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Deposit Synonyms
AUSTRALIAN MANGANESE; BIG; BLUE; EAST WEST MINERAL CO. NL; F.R.J. MANGANESE CLAIM; HORSE SHOE; LAKE; MAGAZINE 1; MAGAZINE 2; MAIN; MCGREGORS LAKE; ML 2774; ML 2776; ML 5787; SOUTH EXTENDED MANGANESE SYNDICATE; TRIBUTORS; WASHER
Mineral District
PERNATTY LAGOON MANGANESE
Deposit Summary
manganese oxide developed as irregular masses & nodules in residual clay, & formed in rudely developed joint system in host Woocalla Dolomite. Production 1915-49 ~34,500t @ 47.5%Mn, 1986 resource estimate 167,500t @ ~20%Mn.
Deposit Description
PERNATTY LAGOON, main manganese workings located on an embayment on the western side of Pernatty Lagoon. The workings were on the lagoon floor, and on the adjacent shore, extending for ~1.7 km. Manganese oxides occurred as irregular masses and nodules of varying size in residual clay, and formed by the decomposition of the manganiferous Woocalla Dolomite. The orebodies tended to parallel a rudely developed rectangular joint system in the host dolomite, with the main orientation being NW. There was a thin cover of lake silt/sand, which made exploration difficult. The main workings included Big Quarry, which was 14 ft deep, covering almost an acre. At Big Quarry the ore was reported as occurring in layers differing in quality, thickness and appearance. The limit of the ore was only reached at the southern end. Most of the workings finished in either ironstone or dolomite. The ore minerals were psilomelane and pyrolusite, and ranged from hard, black, to soft, blue, earthy wad. The harder, higher grade ore was easily upgraded by hand picking. The ore was irregularly distributed over an appreciable area, with estimates suggesting removal of 2 tonne of ferruginous ore and overburden for every1 tonne of manganese ore recovered. Winton (MR31, pp 90) reported a pit sunk to 2 m on natural red ochre (Indian red), and outcropping at the edge of the lagoon within MS 1135. Production from 1915-49 estimated at 34,500 tonne @ 47.55Mn. Remaining resources estimated in 1986 at 167,500 tonne @ 19.6%Mn for cutoff of 10%Mn.
Barite was produced from a narrow 20m wide lode in host Woocalla Dolomite and exposed for ~350m along strike (Fig 8, Bull 41 for location of workings). The lode had irregular bulges, and bifurcated at its northern end. The barite was coarsely crystalline, glassy, white, yellow, pink, with clay-filled joints. The ore was washed to remove clay to provide a product of 98% BaSO4 and up to 2.6% SrSO4. Production included 748 tonne from 1917-24, and 657 tonne from 1938-39. Resource estimate in 1971 was ~160,000 tonne to 10m depth. Prospects for finding more barite were considered to be favourable, with mention of a small outcrop 6km to the south.
Popelka in a paper in the Journal of the Anthropological society of South Australia mentions Pernatty Lagoon as a locale where aborigines mined for red ochre, exact location uncertain. Deep red ochre was found on historic mining section MS 1135. No production records, assays showed high salt content.
Discovery Year
? 1915
Commodities
Manganese, Barite, Ochre
Ore Minerals
Barite, Fluorite, Psilomelane, Pyrolusite
Gangue Minerals
Clay mineral, Goethite, Gypsum, Hematite, Quartz
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