Tungsten Ore Industry Developments-IV

King Island Scheelite Ltd (KIS) is continuing to advance its wholly-owned Dolphin Project, located in Bass Strait on King Island, Tas. The project contains the historic open-cut and underground Dolphin mine, the underground Bold Head mine and a low-grade tailings resource, all of which are being considered by KIS for development. The deposit was discovered in 1911, and comprises tungsten and minor molybdenum mineralisation within scheelite skarns replacing dolomitic metasedimentary units of the Grassy Group. Mineralisation is related to the spatially associated Early Carboniferous granites. Originally mined as an open pit, underground mining commenced at both Bold Head and Dolphin in the early 1970s. Previous mining ceased at both mines in 1990, because of low wolfram prices. A pre-mining resource of approximately 17 Mt at 0.85% WO3 has been determined for the resource4. In 2012, KIS completed a definitive feasibility study investigating both re-treatment of the tailings and re-opening the underground mines. Outcomes of the study include a planned 10–year mine life from both underground mining and re-treatment of tailings, producing 3500 tonnes per annum (tpa) of contained WO3 in concentrate. A review of the definitive feasibility study completed in 2013 advocated shelving of the re-treatment of the tailings, and delaying underground production for several years by concentrating on an identified resource in the existing Dolphin mine open pit floor and walls. A revised study is being undertaken and is due for completion in early 2014. KIS reported in May 2013 that Indicated Resources for the Dolphin open pit remnant, Dolphin underground and the Bold Head Mine, are 0.91 Mt averaging 0.74% WO3, 4.51 Mt averaging 1.28% WO3, and 1.5 Mt averaging 0.93% WO3, respectively, for a combined total of 78.4 kt of contained WO3. Estimates of Probable Reserves for the Dolphin underground mine (excluding the open pit remnant) were upgraded in August 2011 to 2.69 Mt averaging 1.04% WO3 and containing approximately 28 kt of WO3. In June 2011, the company reported Measured Resources for the tailings at the Dolphin Mine at a cut-off grade of 0.08% WO3 as being 2.7 Mt averaging 0.17% WO3. As a result of the feasibility study review, the tailings resource is considered marginal. KIS announced in October 2013 that additional drilling at Dolphin and Bold Head to test previously recognised shallow wolfram mineralisation revealed that, potentially, it was amenable to open-cut mining.

 

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