African gold mine recovered ore valued at US$150,000 in one blast

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

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

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