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

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