Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr
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M A R TA B E M I L L the mining process," Albert said. "There is also Indonesia contractor, Nusa Konstruksi (NKE), which has been with us for six years through development, construction and into operation. NKE's work is lower down in the valley and their basalt quarry generates some nice rock for our tailings facility, for construction as well as general site works. As the mine opens up we may move away from articulated dump trucks to rigid body vehicles but at the moment we have the right equipment for the job." Albert explained that there are different areas at Purnama from where consistent feed is delivered to the plant with the grade, tonnage and material type coming together nicely. "Process plant throughput is going extremely well and the most pleasing aspect is that we are achieving recoveries of better than 90%," Albert said. "We are also ahead of the game with the tailings storage facility and construction is going very well. Executive General Manager Tim Duffy has played a major role in helping us get this far. He has been at Martabe four years, building the operation, shepherding it through construction, and now ramping up operations." facility for mine workers, haulage roads, high voltage switchyard, onsite workshop and warehousing, and a tailings storage facility with associated water catchment and diversion systems. The Martabe plant consists of single stage crushing, semiautogenous grinding and ball milling (with the SAG mill close-circuited with a pebble crusher), and a carbon-in-leach circuit. The cash cost per ounce equation is a work in progress, Albert explained. "We have assessed the consumption of consumables and costs of reagents, labor, etc., and have established a figure of about $450/oz as our guidance for 2013," Albert said. "Most gold industry players are experiencing significant cost pressures so we are pleased to be where we are with cash costs and there are opportunities to improve. We are operating on diesel power but when we get on to the main grid there will be a significant shift downward in terms of our cost structure and we are pushing hard to make this happen as quickly as possible." The electrical infrastructure from the mine to the grid is in place and they are working with the Indonesian power supplier, PLN, to compete the tie-ins. Environmental Concerns and the Community Operations were shutdown in midSeptember owing to an objection being lodged with respect to the discharge of clean water to a river. "The system was approved as part of our environmental approvals but after we were up and running we had some objections from a relatively small part of the 30,000-strong community living around the operation," Albert said. "We are not about to get into conflict with anybody and much prefer to sit down, talk and work through the issues." Martabe has 4 m of annual rainfall and there is a positive water balance with most being rainwater coming off the hills. "The water is contaminated when it enters the tailings storage facility but we use most of it in the processing plant," Albert said. "If there is excess water, we have a highly technical water polishing plant that cleans it to strict environmental requirements and then A New Mine Opens in Indonesia The Martabe mine is the first major mining project to be developed in Indonesia in the last 10 to 15 years. It sits on the western side of Sumatra in Batangtoru sub-district of North Sumatra province. The mine is established under a sixth generation Contract of Work (CoW) signed in April 1997 and which defines all terms, conditions and obligations of G-Resources and the government of Indonesia for the life of the CoW. The Martabe resource base consists of seven known deposits within a 30 km2 area with Purnama the largest so far. Martabe commenced first commercial gold production from the Purnama pit in July 2012. The Martabe mine benefits from a low estimated life-of-mine cost structure for the Purnama pit, which is a result of the capacity and size of the project, the shallow nature of the deposit that results in a low strip ratio of 1.3:1, the good grade of the ore and straightforward gold extraction process. The project is also in a great location, close to highways, airports, port, power and a significant national skilled human resources pool. The Martabe operation encompasses the Purnama open-pit mine, a conventional processing plant with 4.5 million mt/y capacity, a permanent accommodation www.e-mj.com APRIL 2013 • E&MJ; 89