Modern Mining June 2016

WEST AFRICA

capacity can be increased by 50 % at a cost of approximately US$5 million. The flowsheet incorporates primary crushing, grinding with a single stage SAG mill, gravity concentration, classification, leaching and adsorption, tail- ings thickening, electrowinning and smelting. The SAG mill has been upgraded to a 1,5 MW motor (from 900 kW in the Feasibility Study) to allow for added flexibility. The underground mine is accessed by a dual ramp system via a single portal at the bottom of a 23 m deep boxcut. Ramps are designed at a -14,3 % gradient with dimensions ranging from 5,3 m (width) by 5,8 m (height) to 5,0 m by 5,5 m depending on the planned air flows. Longhole open stoping (including up hole retreat in certain areas) is the main mining method with a limited application of cut and fill for the crown pillar mining. All methods except up hole retreat will employ waste rock as backfill. The mine layout is based on 17 m sub-levels. Standard longhole stopes two sub- levels in height (34 m) and 25 m in strike length will be utilised to mine the narrow vein orebody. Ventilation requirements for the mine are estimated at 212 m 3 /s for a production rate of 750 t/d. All of the intake will be through the main access ramp. Exhaust will be through the east and west return air raises, each sized at 3 m diameter. The underground mining contract was awarded to AUMS (African Underground Mining Services) – which has consider- able African experience – in September 2014 although the company only mobilised to site in mid-2015. It is envisaged that by December 2018, AUMS will have delivered 17 100 m of jumbo development, 120 000 m of specialised, narrow-vein, 64 mm longhole drilling and 460 000 tonnes of ore. Yaramoko’s probable mineral reserve totals 1,1 Mt at a grade of 11,83 g/t for 759 000 ounces of gold. The indicated resource (including

reserves) amounts to 1,6 Mt at 15,8 g/t at a 5 g/t cut-off (810 000 ounces) while inferred resources total 840 000 tonnes at 10,26 g/t (278 000 ounces). There is considerable scope to increase the resource base. The current mine plan is to a depth of 430 m but high-grade results have been encountered to a depth of 900 m and there is also potential for lateral expansion of the orebody. In addition, RoxGold has a number of promising regional targets. A high-grade satel- lite resource – QV1 on the Bagassi South permit – was discovered in April last year, 1,8 km south of the 55 Zone (where the underground mine is located). In April this year Roxgold declared a maiden inferred resource for QV1 of 563 000 tonnes at 12,14 g/t for 220 000 ounces of gold at a cut-off grade of 5,0 g/t. Photos courtesy of Roxgold

Celebrating the first gold pour are John Dorward (left), Roxgold’s President and CEO, and Paul Criddle, Chief Operating Officer (photo: Roxgold).

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June 2016  MODERN MINING  29