Milling

LaRonde Concentrator—Description and History

The construction of the original, 1,800 tonne per day, concentrator was completed in 1988. It served to process the ore from open pit #1 and shaft #1, the recovered metals being gold, silver and copper. The mill consisted of the following circuits: crushing, grinding, copper flotation, cyanidation.

Following the discovery of additional deposits on the property which contained gold, silver, copper and zinc, an initial feasibility study relating to the revision of existing circuits was carried out over the course of 1996. Given the ongoing acquisition of geological information, the study was revised at several points, resulting in the expansion of the mill in stages.

September 1997 marked the startup of the revised copper circuit , followed by the implementation and startup of the new zinc flotation and concentrate handling and storage circuits in September of 1998. The new semi-autogenous ball mill was started up in August of 1999. This mill permitted an increase in tonnage to 2,700 tonnes per day before meeting the objective of 3,300 tonnes per day at the end of 1999. This followed adjustments to the various circuits, and the addition of a cyanide destruction and paste backfill circuit.

A second phase was completed over the course of 2000, with the final review of the precious metals circuit. It was modified with the introduction of counter-current decantation and zinc precipitation circuits as well as the addition of a whole new refinery. The mill capacity surpassed 4,500 tonnes per day at the beginning of October 2000.

With the full picture of LaRonde now better-defined, a final increase in throughput to 7,000 tonnes per day was mandated in 2001. The concentrator was in operation at the beginning of October 2002, processing at capacity with the startup of a new secondary grinding circuit.

Today, more than 15 years after the startup of the original mill, the LaRonde concentrator is operating very well, and frequently at greater than design capacity. The mill today includes a new grinding circuit, copper and zinc flotation, a concentrate thickening/filtration and storage area, a precious metals recovery circuit. This circuit combines cyanidation, counter-current decantation, zinc precipitation, and final cyanide destruction prior to paste backfill production.

Milling Flowsheet