Mining at Macassa is currently underway at an average rate of 1,000 tpd across two mining horizons: the historical Main/’04 breaks (20% of the annual throughput) and the new SMC Zone (80% of the annual throughput) with access via #3 shaft. In the Main/’04 breaks, mining is taking place between the 3400 and the 5300 levels. In the SMC Zone, mining will occur between the 5000 and the 5800 levels; the Company will complete the development of a haulage ramp down to the 5800-level elevation in 2017.
Mining is conducted primarily via mechanized cut-and-fill, conventional cut-and-fill and a small portion of long hole methods. All stopes are backfilled with either paste fill, cemented rock fill or loose waste rock. The Macassa Mine was the first mine in the world to use lithium ion battery operated trucks and loaders, which has allowed the Company to maintain its production rate.
The Macassa Mill was constructed in 1986, originally designed for a throughput of 725 tonnes per day. The mill underwent additional expansions and was upgraded to handle 2,000 tpd. Processing of ore at Macassa starts with crushing and grinding the ore to a particle size of 45μm before it enters the leach tanks for cyanidation. Then, it flows through a carbon-in-pulp (CIP) circuit, followed by a Merrill-Crow recovery system. The concentrate is melted in an inductotherm induction furnace where doré is poured and typically contains 85% to 88% gold.