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The Redbank and Azurite prospects were discovered by William (Bill) Masterton in 1916. It is estimated that 800 tonnes of copper oxide were mined by Masterton prior to his death in 1961. The ore was hand-sorted and transported to the coast by packhorse. In 1966 Granville Development mined 2,000 tons, which was sent to Mount Isa for processing.
Prospecting continued at Redbank, including a geophysical survey undertaken in 1967 by Placer Prospecting Pty Ltd. Confirmatory drilling was subsequently undertaken by Harbourside Oil NL in 1970, during drilling high grade copper sulphide ore was encountered beneath an equally high grade oxide cap at the Sandy Flat prospect.
The Westmoreland-Harbourside-Newaim joint venture undertook further drilling, geophysical surveys and geological mapping in 1971. The joint venture was dissolved at the end of 1971, as the reserves did not meet their corporate requirements.
Hydro-metallurgical testing was undertaken at Sandy Flat in 1981 by Triako-Buka-Amdex. Sandine-Restech-Hunter Resources-Vanoxi subsequently took control of a reduced area in 1983, and Exploration Retention Lease (ERL) 94 was established to protect the Sandy Flat area.
Redbank Copper Pty Ltd purchased the tenement group from Sanidine-Vanoxi in December 1989. Following further drilling programs and metallurgical testing, a Preliminary Environmental Report was submitted and assessed under the NT Environmental Assessment Act (EA Act) in 1993. A mining approval was consequently granted in 1994.
Mining and associated processing was undertaken between 1994 and 1996. The ore was processed through conventional floatation methods to produce a copper concentrate. Operations continued for approximately two years at the site, until copper prices dropped and the take-off customer, Mt Isa Mines, was no longer willing to accepting the concentrate. The last mining occurred in June 1996 and at this time the site was placed in care and maintenance.
Following the cessation of mining activities, an estimated 54,000 tonnes of partially treated and potentially acid forming material remained stockpiled on the surface at site. In 2004 a heap and vat leach extraction process was established at the site, this process consisting of placing crushed ore in lined vats and leap leach pads. A recycled acidic solution, of pH 2 to 3, was used to irrigate the ore and leach the copper.
In early 2006 the Redbank Project was acquired by Burdekin Pacific and the name of the company operating the site was changed to Redbank Mines Limited. Production was ceased during the 2005/2006 wet season, however, recommenced in 2006/2007. During this period stockpile material was treated using a similar leaching process as outlined above, however, on a smaller scale. It should be noted that there has been no significant production at the site since 1996.
Further exploration was undertaken by Redbank Mines Limited between 2006 and 2008 to verify the results of the 1971 exploration. A pre-feasibility study was completed in November 2007, and a definitive feasibility study was undertaken in 2007 and 2008.
In 2009 the site was again placed in care and maintenance. At this time Redbank Mines Limited was renamed Redbank Copper Limited.
Redbank Copper Limited submitted an Environmental Impact Statement (EIS) for the expansion of the Redbank copper operations in 2009. Redbank Copper Limited proposed to expand the current infrastructure at the Sandy Flat Mine, including commencing processing using a new tank leach solvent extract electro winning plant, and mining of the Bluff, Azurite and Redbank deposits. In addition, a new tailings storage facility (TSF) and waste rock dumps were proposed.
Due to insufficient detail being provided in the EIS, supplementary information was requested. Supplementary information was consequently provided to the Department of Natural Resources, Environment the Arts and Sport in February 2010. The supplementary information proposed excluding mining and processing of sulphidic ores and the TSF from the assessment proves. An application for these components was to be resubmitted once sufficient information was available.
Approval for mining of oxide ore from the Redbank, Azurite and Bluff deposits was granted in April 2010. However, Redbank Copper Limited deemed the project uneconomic and the site has remained in care and maintenance. On-going exploration has been undertaken during the care and maintenance period.
Redbank Copper Limited currently holds ERL94, and five mineral leases. These are Mineral Lease Northern (MLN) 631, MLN 632, MLN 633, MLN 636 and MLN 1108 and cover an area of 65.44 ha. It is noted that the Sandy Flat Mine is located on MLN 636, MLN 633, and MLN 1108.