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62 E&MJ; • APRIL 2017 www.e-mj.com OPERATING STRATEGIES During the three months to end-Decem- ber 2016, most of the major gold mining companies reported a reduction in all-in sustaining costs, or AISC, compared with the previous quarter. Supported by the implementation of asset restructuring and improvement initiatives throughout the year, the gold majors managed to re- duce AISC on the basis of both a quar- ter-on-quarter and year-on-year analysis. The top 19 publicly listed gold com- panies that reported AISC produced gold at a weighted-average cost of $868/oz, slightly lower than the $889/oz in the third quarter, according to data from the SNL Metals & Mining database, an offer- ing of S&P; Global Market Intelligence. Centerra Gold, which reports AISC on a by-product basis per ounce sold, was the lowest-cost gold producer in the group with AISC of $586/oz. According to Scott Perry, Centerra's CEO, the com- pany's favorable cost performance during 2016 can be attributed to the higher mill production and lower unit costs at the company's fl agship Kumtor mine, com- pared with the previous year. Barrick Gold had the third-lowest gold AISC in the December quarter at $732/ oz. For the year as a whole, the precious metals producer managed to reduce AISC to $730/oz, recording a 12% drop year on year. Barrick continued to strengthen its balance sheet, reported SNL, cutting debt and executing business development ini- tiatives throughout the year. Continuing the trend, the company recently announced that it was consolidating its main assets in Nevada and expects to reduce gold produc- tion costs at its operations by $100/oz. The top ten producers in terms of low- est reported AISC ($/oz), according to the SNL survey, included: • Centerra Gold ($586) • Evolution Mining ($674) • Barrick Gold ($732) • Goldcorp ($747) • Newcrest Mining ($751) • Northern Star Resources ($796) • Agnico Eagle Mines ($832) • Buenaventura ($846) • Kirkland Lake ($875) • Gold Fields ($911) The highest reported AISC numbers were from Harmony Gold Mining ($1,129), Detour Gold ($1,124) and AngloGold Ashanti ($1,047). Median Q4'16 AISC, as reported by SNL, was $911/oz. Grade Control Here are some current examples of how gold producers are implementing technol- ogies to cut costs, improve operational ef- fi ciency and reduce potential — and prob- ably costly — environmental impact from their mining and exploration activities. Maptek, for example, recently de- scribed how its Vulcan 3D mine planning and modelling software is used for grade control in a bulk mineable Carlin-type gold system at the Cortez Hills mine in Nevada. Jennifer Baar, senior ore control ge- ologist; and Patrick Ruffridge, resource geologist at the Cortez Hills operation, explained in the March 2017 issue of Maptek's online newsletter Forge that the mine, located on the Battle Mountain-Eu- reka Trend and operated by Barrick Gold, is a uniquely mineralized Carlin-type depos- it. Carlin-type deposits are sediment host- ed, disseminated gold systems associated with arsenic and thallium. Typically, these structurally complex deposits are located along range-front faults and are silicifi ed; alteration at Cortez is decalcifi cation. Cortez Hills has several related, but geometrically distinct orebodies being mined via both open pit and underground operations. Within the open pit operation, there are three distinct areas of mineral- ization in one pit; continuous mining oc- curs across the deposit boundaries. Each deposit has its own structural orientation (attitude) and thus requires specifi c esti- mation parameters for ore routing. Cortez is a historic silver mining dis- trict dating back to the 1860s. Gold min- ing in the district began in the 1960s on a small scale and in the 1990s moved into large scale, bulk gold mining with Placer Dome. Barrick acquired Cortez in 2006. Since around 2009 Cortez Hills has used Maptek Vulcan for daily grade con- trol processes. The authors note that in 2016 the Ore Control group upgraded from Vulcan 9 to Vulcan 10 and began seeing immediate results in block outs. Cortez Hills Open Pit engineers and geologists import blasthole samples from the acQuire database interface into Vulcan by blast pattern name. Each pattern has a unique ID and contains around 75 to 120 offset drillholes. Once imported, blastholes are compared to a preset grade control clas- sifi cation using a grade control scheme fi le. The loaded blastholes are color coded into pre-designated bins based on grade All-in Gold Costs are Coming Down, and Here's How Technology Can Help Cortez Hills open pit with different deposits depicted by color.