Rockcliff Metals Corporation has announced results from ore sorting test work indicating high potential for the use of ore sorting to preconcentrate mineralised material from the 100%-owned polymetallic VMS Tower and Rail (Cu, Au, Ag, Zn) deposits located in the Flin Flon-Snow Lake region of Manitoba. The company is also evaluating a low cost-in-mine haulage system, such as Rail-Veyor, for the planned mines, which will use the Bucko Mill facility which is 130 km and 185 km away from the Tower and Rail projects, respectively.

The Flin Flon-Snow Lake greenstone belt, Manitoba, home to the largest Paleoproterozoic VMS district in the world hosting mines and deposits that contain copper, zinc, gold and silver. Alistair Ross, President and CEO commented: “The ore sorting characterisation test work on our Tower and Rail deposits provides exciting upside for our projects on a number of fronts. With an upgrade ratio of at least 1.4 on both Tower and Rail, ore sorting has demonstrated an ability to reject low sulphide waste.

The advantages Rockcliff sees include the following:

• Both ores responded similarly to ore sorting and flotation test work, supporting the hub and spoke strategy for utilising the same mill and sharing capital between succesive mines;
• Mining dilution, a serious issue for narrow vein mines, is now a manageable cost by using low cost ore sorting and a low cost-in-mine haulage system, such as Rail-Veyor, that Rockcliff is actively investigating;
• Transport costs from the mine sites to the mill will be substantially decreased by keeping the waste rock at site for backfill purposes;
• Milling costs will be substantially reduced by eliminating the waste rock from the mill stream; and
• Tailings impoundment volumes will be substantially reduced by placing the waste in the mine.

Ross adds: “I look forward to seeing these multiple benefits of ore sorting reflected in our combined Tower and Rail PEA which is currently underway.”

Coarse crushed samples from Rockcliff’s Tower and Rail deposits were selected by hand from five near surface diamond drill holes at Base Met Labs in Kamloops, BC and sent for sorting amenability testing at the Steinert facility in Kentucky. About 400 individual samples were selected to represent both local host rock (waste/dilution) and the mineralised target areas across the two deposits.

The individual fragments ranged in size from 10 mm to 40 mm and each piece was initially scanned prior to a scoping level bulk sorting demonstration using X-ray transmission (XT) technology. The advantage of using XT for the ore sort is that this sorting technique requires very little material preparation and is insensitive to moisture or dust coatings on the particles.

A preliminary bulk sorting demonstration was also completed for each deposit. The sorting test was conducted in two stages: first at a high sensitivity to generate a high-grade, low mass concentrate and second at a lower sensitivity to capture the residual sulphide material in the sample. For Tower, over 99% of the metals were recovered to 67% of the mass, and for Rail over 98% of the metals were recovered to 68% of the mass.

Metal grades at both deposits were increased by almost 50% from expected mining diluted grades. The mass balances suggest that sulphide material was pulled into the concentrate from the host/dilution rock and that non-sulphide material was rejected to the waste stream from within the mineralised envelope. Sorting technology has strong potential for industrial application to upgrade mined Tower and Rail material prior to transport to the mill. “This will benefit both projects through rejection of low value waste or mine dilution and lower overall transportation costs with better mill feed grades all contributing to improved project economics.”

Rockcliff has a six year lease on the Bucko Mill and tailings facilty located within trucking distance from its portfolio of Snow Lake deposits.   Metallurgical test work has been designed in two phases. The first phase has demonstrated  the ability of the ore to respond to concentration by flotation. The second phase will focus on the optimisation of the concentration process through the Bucko Mill.  This  will enable Rockcliff to evaluate the potential of mill upgrades and the economic trade-off of capital required for this optimisation. The phase II work schedule has begun and is to be completed as part of the PEA studies for the Rail and Tower properties anticipated to be completed in Q3 2020 in anticipation for a construction decision on one of the two deposits.