The Asia Miner

JAN-MAR 2016

The ASIA Miner - Reporting Important Issues to Mining Companies in the Asia Pacific Region

Issue link: https://asiaminer.epubxp.com/i/632337

Contents of this Issue

Navigation

Page 22 of 59

Volume 13 • Issue 1 | 2016 | ASIA Miner | 21 Indonesia METALLURGICAL test work at Augur Resources Wonogiri Gold-Copper Project in Central Java suggests that a coarser grind size could result in improved gold recovery while also reducing grinding time and lowering operating costs. The tests were carried out on minus 75 micron to minus 106 micron grind sizes with re- sults were compared to the previous minus 53 micron grind. Processing of single composite sample ground to minus 75 mi- cron indicates that 43.7% gold recovery can be achieved via grav- ity concentration using a Falcon concentrator and when combined with intensive cyanide leaching of the gravity tailings, a total of 88.3% gold recovery is possible. Additional testing is in progress on four bulk grinds to confrm gold recoveries via gravity concentration and intensive cyanide leaching of both concentrates and tailing. Based on results to date the option of a gravity and intensive leach of gravity concentrate and tailings fowsheet appears to be techni- cally viable with very good leaching characteristics for little preg-rob- bing minerals reporting to the gravity (Falcon) concentrate. Several processing fow-sheet scenarios are being evaluated in- cluding gravity concentrations followed by intensive cyanidation to treat the gravity concentrate. The loaded solution produced from the leach reactor would then be fed to a conventional electro-win- ning cell bank before being conventionally smelted to produce gold doré bullion. Leaching of the more voluminous gravity tailings would require a larger carbon-in-leach circuit. General ASTM standard rock quality tests of potential aggregate in the area selected for development of a standalone quarry were completed at PT Geoservices laboratory in Bekasi, West Java. Tests were completed on six bulk rock samples made from drill core composite samples collected from three holes drilled within the pro- posed quarry area. Results indicate that the rock has the properties required to be highly suitable for a variety of stone aggregate uses including concrete. It is clear from the earlier market study and related discussions with industry consultants that there is strong demand for high qual- ity aggregate in Java to supply ongoing and planned infrastructure projects as part of an extensive transportation upgrade initiative by the government. The company is evaluating several aggregate pro- duction scenarios with interested contractors who would provide quarry development and production management services. Augur has also completed initial drilling comprising six holes for 781 metres on defned copper and gold targets at Toluludu and Tapadaa prospects at the Gorontalo project. Results indicate that additional drilling is warranted within both areas. SINCE commencing operations in mid-October at the Derewo River Gold Project of West Wits Mining in Papua Province, site manage- ment has focused on developing the most effcient circuit for mining the 81 Creek alluvial gravels. This has involved testing the optimum set up of the sluice boxes to maximise effciency, testing process- ing systems such as water cannon and venturis, and training local community members to operate the circuit. As a result management has developed a comprehensive practi- cal understanding of the specifc issues involved in mining the area. It is evident that mining this gravel sequence will require the employ- ment of various operational methods to deliver optimal recoveries. For example, a water cannon is proving effcient at moving the gravels but the many in situ boulders require deployment of heavy equipment to clear a path. In addition the basement potholes, which tend to be higher in grade, are not amenable to mining through either of these mechanical methods and will need to be cleared out manually. Thus far, this trial and commissioning phase has been conducted in the lower part of the 81 Creek where extensive artisanal mining has been undertaken for up to 10 years. These low grade gravels were initially targeted as they allowed management to gain con- fdence in the circuit without risking loss of higher grade gravels before moving to full production. The frst stage of full-scale mining is planned to commence at a location higher up the creek which should permit access to thicker and less mined gravels. The gravels are about 12 metres thick in this area and access points are dictated by the basement profle and topography. After operations were closed for a short Christmas break, com- mencement of full mining has been scheduled for the week be- ginning January 4 preceded by a planned feast ceremony with the local community to mark the start of full operations. Whilst operations have proceeded without interference a large number of illegal miners are operating in close proximity. These peo- ple continue to illegally remove gold and their presence constitutes an ongoing threat to stability and security. West Wits' new Indone- sian partner for the venture PT Intan Angliasa Aviation is continuing efforts to procure removal of the illegal miners but is yet to defne a clear timeline to achieve that goal. The pleasing progress at Derewo must be tempered with caution until all unauthorised persons have been removed. Operations under way at Derewo River Sorting ore samples at Augur Resources' Wonogiri Cold-Copper Project in Central Java. Coarser grind considered at Wonogiri

Articles in this issue

Archives of this issue

view archives of The Asia Miner - JAN-MAR 2016