Breakwater targets Caribou for treatment process testing

It is not uncommon for a mine to be shut down and later reactivated as a result of technological advances. Such may be the case with the Caribou polymetallic mine near Bathurst, N.B.

Owned by Breakwater Resources (TSE), the mine operated briefly in 1990 before closing for reasons related to the complex metallurgy of the lead-zinc-copper-silver-gold mineralization.

During its seven months of operation, the Caribou mill produced a low-grade bulk concentrate containing 35% zinc, 8% lead, and 216 grams silver per tonne. Metal recoveries from the concentrate were 72.8% for zinc, 33.6% for lead and 28% for silver.

“The market for this bulk concentrate was weak, and economic conditions could not support a mining operation,” says Breakwater Vice-President Colin Benner, Recently, the company engaged Lakefield Research to develop a treatment process that can enable the production of separate, marketable lead and zinc concentrates with respectable recoveries.

Lakefield has demonstrated that production of a zinc concentrate is now possible, as is a separate lead and precious metals concentrate. Results from bench tests show the zinc concentrate contains 52-55% zinc, of which 80-85% is recoverable.

The lead concentrate, which also contains precious metals, averages 52-55%, of which 70-73% is recoverable. In addition, the concentrate contains 1,100 grams silver and 1.37 grams gold per tonne. Silver recoveries were reported to be 48.8%, while no figure for gold recovery was provided. Breakwater is also examining ways to capture the copper contained in the ore. Lakefield’s mill consists of typical grinding and flotation circuits. Commercially available reagents are used to separate and float off the zinc-rich concentrate from the lead and precious-metals-rich concentrate. Breakwater intends to run two pilot tests at the Lakefield mill, using 150 tonnes of ore in the first test and 50 tonnes in the second. The tests are expected to start later this month, and be finished within four weeks. Pending successful results, Breakwater will proceed with a final feasibility study for reopening the mine.

The Caribou has proven, probable, possible and inferred reserves of 13 million tonnes averaging 8.18% zinc, 3.52% lead, 0.38% copper, and 102 grams silver and 1.4 grams gold.