In mid-2016, the geology and processing teams at Bald Mountain noticed a change: the cyanide solution was percolating through the heap leach pads slower than anticipated.
Isaac Amponsah, Chief Metallurgist, Bald Mountain, suspected that there was a higher portion of fine material in the new ore, which was causing the slowdown, since the site regularly tests the ore for particle size. “The fine materials fill up the empty spaces between the rocks and prevent the solution from flowing as quickly as we’d like it to, which could potentially delay gold production,” said Issac.
The Bald Mountain team looked to the experiences of other Kinross heap leach operations in search of a solution. A similar issue encountered at Round Mountain’s Gold Hill pit was solved by blending ore. The team at Bald Mountain thought that the same approach could also solve their issue and used the ‘Achieving Excellence’ program to evaluate the impact of blending on both mining and site economics, and decided to move forward with its implementation. It’s been nothing short of a team effort to make it happen.
To make sure this approach would be successful, the team knew they needed their shovel operators to keep a close eye on the ore they were mining. “Our geologic models give us a good sense of where we will find material that’s good for blending,” said Darren Parsons, Senior Geologist, Bald Mountain. “But, it’s the shovel operators who are watching every bucket they place in a truck.”
Darren has been instrumental in training the mine operations team to identify the different types of material that would be ideal for blending and working with the field supervisors to make sure that it goes to the right heap leach pads.
“The crews have done a great job of making sure blending is going as planned,” continued Darren. The strategy has to be coordinated and executed perfectly because stockpiling must be avoided whenever possible.
“One of the challenges with mining a low grade run-of-mine deposit is that even minor additional costs can really cut into our profit margin,” added Tom Fedel, Senior Mining Engineer, Bald Mountain. “We’ve adjusted our mine plans so that we can get different types of material from different parts of the pit at the same time. Then we blend them when they’re dumped on the pad and avoid incurring any extra costs.”
The coordinated effort across multiple departments has been worth it: since instituting the blending strategy, percolation rates through the pads have improved and are consistently being maintained. The strategy has also helped the site team generate more accurate production forecasts.
An example of ore with a high percentage of fines (left) compared to good “no blend” ore (right)
Gregory Snow, Generation Gold Geologist, Bald Mountain, inspects a hand sample of ore for fine material