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Accounting for blast movement generated US$215,000 in one blast for this low-grade, disseminated-ore gold mine.

This mine blasts its soft, sedimentary rock-hosted deposits using a low powder factor to achieve fragmentation, and mines 20 to 40 ft benches a single pass.

Even with the low powder factor, the grade control team identified that dilution was negatively affecting reconciliation, and that mid-bench blast movement contributed to ore loss; resulting in gold being sent to the waste pile. As a result of accurately measuring blast movement and translating post-blast dig lines, this major gold producer recovers more ore and reduces dilution – every blast.

Significant movement occurs within all blasts and variation of ±50% from the mean horizontal movement is common and occurs at this mine. In this example blast, measured horizontal movement ranged from 3 to 14 ft and vertical movement was up to 3 ft (1 m).

By accounting for the 3D movement in this blast, the mine added US$215,000 of value:

• avoided unnecessary milling costs of US$135,000 and 4,500 tons of waste being treated as ore – reducing dilution by 9%, and
• recovered an additional 2,900 tons of ore, valued at US$80,000, increasing ore recovery by 5%.