African gold mine realised US$150,000 additional value

African gold mine realised US$150,000 additional value

Commodity Ore Grade Geology Powder Factor Flitches Location
Gold 2.2 g/t** Structured 0.85 kg/m3 4 Africa

 

This gold mine is one of the top producing open-pit gold operations in West Africa.
  • Mineralisation is shear-hosted in sedimentary deposits
  • Blasts are fired in 10 metre (33 ft) benches and mined in four flitches (2.5 m)
  • The site contains high grade (above 2.2 g/t) ore

Challenges

Polypipe solution failed to identify significant mid and bottom bench post-blast ore movement
  • The site had tried to use polypipe (BVIs) to measure blast movement
  • Recovery of the pipes was poor
  • Polypipe data did not accurately measure the bulk movement of the blast because the surface moved much less than mid- and lower-bench
  • The resulting ore loss contributed to a continued drop in reconciled head grade

Solution

The BMM System accurately measured blast movement and translated post-blast dig lines
  • 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 ore loss and dilution that would have occurred without monitoring

Results

US$150,000 additional value by accurately accounting for blast movement after one blast
Significant movement occurs within all blasts. Variation of ±50% from the mean horizontal movement is common and occurs at this mine.
  • Measured horizontal movement ranged from 0.3 to 5.7 m (1 to 19 ft) and vertical movement of up to 3.5 m (11 ft)
As a result of accurately accounting for blast movement, the mine:
  • Reduced dilution—1,500* tonnes of waste were diverted from the mill, avoiding $20,000**** of unnecessary milling costs
  • Maximized ore yield—recovered an additional 1,500 tonnes of ore, valued at US$130,000***
* Numbers are rounded
** Average grade of ore polygons
*** Calculated at a gold price of US$1,250/oz
**** Based on milling costs of $16 per tonne
Accounting for blast movement in one blast added US$150,000 of value
Africa gold mine translated ore polygons flitch 2 Post-blast ore loss and dilution varied from 35 – 40% in the top flitch to 40 – 65% in the lower flitches.
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