This operation is one of the top producing open-pit silver mines in the world.

• Deposits are structurally-controlled in low to medium sulphide veins
• Drills and blasts 7.5 m benches, mined in a single pass
• Contains high grade (60 g/t) silver mineralisation with gold as a by-product

Challenges

Selective mining in a structurally-controlled deposit generated reconciliation issues when ore polygons move outside their original boundaries

• Ore loss: unaccounted blast movement means material containing high grade silver ore is sent to the waste pile
• Dilution: tonnes of waste are unintentionally sent to the mill
• Misclassification of ore: high grade ore is stockpiled as low grade or low grade ore is sent to the mill as high grade

Results

Significant increase in ore recovery adds $260,000 of value—in 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 7.3 to 10.5 m (24 to 36 ft) and vertical movement of up to 1.4 m (5 ft)

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

• Maximized ore yield—6,100^* tonnes of ore were recovered, valued at US$200,000^*** (avoided 30% ore loss)
• Reduced dilution—6,000 tonnes of waste were diverted from the mill, resulting in 30% dilution and $60,000^**** of unnecessary milling costs
• Prevented misclassification—1,200 tonnes (6%) of ore would have been misclassified

* Numbers are rounded
** Average grade of ore polygons
*** Calculated at a silver price of US$19/oz.
**** Calculated from milling costs of US$10 per tonne