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North American gold mine adds $215,000 of value

Commodity Ore Grade Geology Powder Factor Location
Gold 0.025 oz/ton* Disseminated 0.33 lb/yd3  North America

This low-grade, disseminated-ore gold mine is one of the top producing open-pit operations in the world.

  • The mine drills 20 or 40 ft (6 or 12 m) benches that are mined in a single pass
  • Current grade control method uses blast hole assays to create an ore control model
  • The soft, sedimentary rock-hosted deposits (density 0.07 ton/ft3) require a low powder factor to achieve sufficient fragmentation

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Challenges

Blast movement did not appear to be a contributing factor to poor ore yield
  • Measurable dilution negatively affected reconciliation despite the low powder factor used in the pit
  • Mid-bench blast movement contributed to ore loss, with gold being sent to the waste pile

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, and areas of ore loss and dilution that would have occurred without monitoring

Results

Less dilution and more ore—additional $215,000 of value in this 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 3 to 13.5 ft (1 to 4 m) and vertical movement of up to 3 ft (1 m)

As a result of accurately accounting for blast movement, this mine:

  • Avoided unnecessary milling costs of US$135,000,1,2 reducing dilution by 9% and avoided 4,500 tons (4,100 tonnes) of waste being treated as ore
  • Recovered an additional 5% of ore, 2,900 tons (2,630 tonnes), valued at US$80,0003

* Average grade of ore polygons
1. Numbers are rounded
2. Estimated from mine milling costs of US$30 per ton
3. Calculated at a gold price of US$1,250/oz.

Accounting for blast movement generated US$215,000 in one blast

North American gold mine adds $215,000 of value

BMT