July 18, 2013
- Positive results from various metallurgical options considered for the Twin Metals Minnesota Project
- Good metal recoveries to both a bulk concentrate and to separate copper (~25% Cu, <1% Ni) and nickel (~10% Ni, <5% Cu) concentrates were achieved during recent pilot plant programs;
- Good metal extraction from bulk concentrate using the CESL™ process;
- Good recoveries of gold and platinum group elements from CESL™ residues by sulfur flotation.
Duluth Metals Limited ("Duluth Metals") (TSX: DM) (TSX: DM.U) is pleased to announce significant progress on various metallurgical options being considered during pre-feasibility on the Twin Metals Minnesota Project ("Twin Metals"). Some of the most recent test results from an ongoing comprehensive metallurgical testwork program aimed at defining the optimal process flowsheet for the recovery of copper, nickel, gold, platinum, and palladium to payable products are summarized below. This metallurgical testwork program involved mineralogical assessments, laboratory bench scale testing, and pilot plant testing with independent laboratories.
The metallurgical testwork included flotation programs to develop and prove two separate flotation options: the first being the option to produce a bulk copper-nickel concentrate; and the second option being to produce a marketable copper concentrate and a marketable nickel concentrate.
Testwork was conducted on both the bulk concentrate and the nickel concentrate using the CESL™ process. Teck Resources Limited ("Teck") has developed the CESL
hydrometallurgical process that effectively recovers copper, nickel and PGM's from bulk copper-nickel-PGM concentrates, which
and Twin Metals are considering as a concentrate processing alternative. Both concentrates from the Maturi group of deposits have been successfully processed at bench and pilot scale at Teck's hydrometallurgical facility in
More detailed summary reports for the two approaches (selective flotation and CESL
processing) are available on the Duluth Metals website at
, President of Duluth Metals stated, "This metallurgical test work is quite encouraging. The Twin Metals project now has two viable processing alternatives for the project that can be evaluated during the pre-feasibility. The pilot plant work has shown that either a CESL™ process or production of marketable flotation concentrates can be effectively operated with the Twin Metals resource."
The test programs were conducted to establish initial parameters for engineering design of the Twin Metals processing plant. One important component of the program was a flotation pilot plant campaign at the ALS Metallurgy facility in
, where Maturi material derived from drill core was processed to demonstrate both bulk concentrate and separate concentrate flowsheets. The flotation test work was successful at demonstrating the ability of the flowsheets to achieve high base and precious metals recovery to either a bulk concentrate or to separate copper and nickel concentrates,
A second component of the test work included a six week pilot plant operation of the CESL™ process at Teck's hydrometallurgical facility in
Richmond, British Columbia
. CESL™ work established good overall recoveries of metal into three products: cathode copper, a mixed (nickel and cobalt) hydroxide, and a precious metals flotation concentrate.
Head grade assays are supported by the Resource Estimate, and verified under the standard QA/QC program of the respective independent commercial laboratory responsible for executing the metallurgical testwork program. Similarly, the actual testwork protocols, sample collection, assay reconciliation, and metallurgical balance at laboratory scale and pilot plant level are all developed under each commercial laboratory's standard QA/QC protocols.