This African copper mine operates three active open pits. The predominant mineralisation is structural in nature and is found in a narrow-vein which dips differently in each pit.

• Ore polygons are delineated using assay data taken from reverse-circulation drilling performed prior to blast hole drilling
• Blasts are relatively narrow (max width ~25 m (80 ft)), highly confined on both sides and in the front face
• The site mines two flitches of 3 m (9 ft) each on a 6 m (18 ft) bench

Challenges

Lack of accurate blast movement data from BVI solution

• The site had tried to use BVIs (poly-pipes) to measure blast movement
• Recovery of the pipes was poor; mine personnel successfully recovered only one BVI per month
• Polypipe data did not accurately measure the bulk movement of the blast because the surface moved much less than mid-bench

Results

Less dilution and more ore—added US$286,000 in one blast

Significant movement occurs within all blasts. Variation of ±50% from the mean horizontal movement is common and occurs at this mine.

• Mid-bench horizontal displacement was 1.0 m to 11 m (3 to 36 ft). Vertical movement was measured as up to 6.0 m (19 ft), 1.6 m (5 ft) at the flitch boundaries

By accounting for blast movement accurately, this mine:

• Avoided sending ore to the waste dump—3,400^* tonnes (27%) in the top flitch and over 1,800 tonnes (14%) in the bottom flitch
• Reduced dilution of 421 tonnes
• Generated US$286,000^*** additional value in this blast

* Numbers are rounded
** Average grade of ore polygons
*** Calculated at a copper price of US$5,500/t