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West African gold mine reduces misclassification

west africa gold mine

Commodity Ore Grade Geology Powder Factor Flitches Location
Gold 1.2 g/t* Structured 0.6 kg/m3 2 West Africa

This gold mine is one of the top producing open-pit gold operations in West Africa.

  • The ore deposits are structurally controlled conglomerate reefs, which are separated by quartzite waste rocks
  • Operations are carried out over two pits, currently mined in two and three 3-metre flitches
  • The site contains low and high ore grades

Challenges

Visual controls did not prevent post-blast ore type misclassification
  • Deposits were visually controlled
  • Significant misclassification was occurring, with high grade ore blocks moving into low grade ore blocks after blasting, and vice versa

Solution

BMM System accurately tracks 3-dimensional ore block movement, mitigating ore type misclassification
  • Blast movement monitors (BMMs) were installed in monitoring holes throughout the shot
  • Installation and detection as per site standard operating procedures
  • BMM Explorer software calculated new dig lines for each flitch and areas of misclassification, ore loss and dilution that would have occurred without monitoring

Results

Less misclassification of high and low ore grades
Recovered US$250,000 in one blast

Significant movement occurs within all blasts. Variation of ±50% from the mean horizontal movement is common and occurred in this example blast.

  • Horizontal movement, recorded by BMMs, ranged from 3.5 – 6.4 m and vertical movement was up to 3.0 m

As a result of accurately accounting for blast movement, this mine:

  • Prevented ore type misclassification—3,4801 tonnes would have been sent to the wrong destination
  • Maximized ore yield—recovered an additional 200 oz (5,400 tonnes of ore), valued at US$250,0002
  • Reduced dilution—3,800 tonnes of waste was diverted from the mill, saving $US68,4003 in unnecessary milling costs

* Average grade of ore polygons
1. Numbers are rounded
2. Calculated at a commodity price of US$1,250/oz.
3. Calculated on mill processing cost of US$18 per tonne

From the top flitch, this gold mine recovered 3,120 t of ore and avoided 11% misclassification