Duluth Metals Provides Metallurgical Update on Twin Metals Minnesota Project
TORONTO, July 18, 2013
TORONTO, July 18, 2013 /PRNewswire/ --
*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
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 ^[ ^TM ^] hydrometallurgical process that effectively recovers copper,
nickel and PGM's from bulk copper-nickel-PGM concentrates, which Duluth 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
Richmond, B.C. More detailed summary reports for the two approaches (selective
flotation and CESL ^[ ^TM ^] processing) are available on the Duluth Metals
website at http://www.duluthmetals.com .
Vern Baker, 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
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 Kamloops BC, 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
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.
I. SELECTIVE FLOTATION
Twin Metals has been working since early 2012 on a comprehensive metallurgical
testwork program aimed at defining a commercially viable process flowsheet
that will recover copper, nickel, gold, platinum, and palladium to payable
products. This metallurgical testwork program included mineralogical
assessments, laboratory bench scale testing, and pilot scale testing.
A variety of samples have been tested as part of the metallurgical test
program. In particular to the flotation flowsheet development and pilot plant
programs undertaken in 2012 and 2013, the majority of samples were obtained
from a large PQ drilling campaign which acquired almost 70 tons of mineralized
Two flotation flowsheets were investigated. The two flowsheet circuits
considered primary grinding and multi-stage flotation including rougher,
regrinding of the rougher concentrate and two or three stages of sequential
The first flowsheet involved production of a bulk concentrate that would
require onsite processing rather than direct sale to smelters. Results of the
bulk flotation showed very high copper recoveries and solid nickel recoveries.
Concentrate grades and recoveries can be found in the summary reports
available on our website.
The second flowsheet (selective flotation) involved production of a marketable
copper concentrate and a marketable nickel concentrate. The sequential
flotation tests indicated very little loss of copper recovery and minimal
nickel recovery losses in comparison to the production of a bulk concentrate.
Testwork indicated that nickel deportment to the copper concentrate was
minimal. Copper concentrates of almost 25% copper with less than 1% nickel,
and nickel concentrates of approximately 10% nickel with less than 5% copper
were achieved. Ongoing testwork is focused on upgrading the nickel content of
the nickel concentrate. Specific values and trends are represented in the
summary reports available on our website. Note that these results were
achieved during bench and pilot plant programs using the composite ore samples
as described above; additional testwork programs are planned to investigate
variability in ore response to the flotation flowsheet as a mine plan is
developed for the deposit.
II. CESL™ TESTING
Three concentrates from the Twin Metals project were successfully processed
through Teck's hydrometallurgical research facility utilizing the CESL™
process for approximately a six week period in Q1 of 2013. The concentrates
processed through the pilot plant consisted of three different concentrates
from the Twin Metals resource. The first concentrate was a bulk concentrate
(all metals floated in one concentrate) made from a mixed sample of material
from the Maturi and Birch Lake deposits. The second concentrate was a bulk
concentrate made from material derived from the western portion of the Maturi
deposit. The third concentrate was a nickel concentrate derived as one of two
products from the ALS flotation pilot plant during the period when a separate
copper and nickel concentrate was being produced from ore from the western
portion of the Maturi deposit.
The concentrate characteristics were:
*Maturi Bulk #1 - produced from Maturi East and Birch Lake deposits (17.0 %
Cu, 3.7 % Ni and 20.4 g/t TPM (Total Precious Metals or TPM =
*Maturi Bulk #2 - produced from Maturi West deposit (15.5 % Cu, 4.1% Ni and
9.0 g/t TPM);
*Maturi Ni-Cu - produced from Maturi West deposit after separation of a
high grade Cu concentrate ( 6.9 % Cu, 8.0 % Ni and 10.6 g/t TPM).
The main goals for each of the concentrates were to determine optimal base
metal extraction while also recovering precious metals. Multiple variables
were tested in the leaching circuits to determine the optimal operating
conditions for recovery of metals.
Overall CESL™ pilot plant metal recoveries from concentrate are presented in
Table 1. The results for the two bulk samples are combined due to limited run
time for the second sample.
Table 1: Maturi Metal Recoveries from Concentrate
Concentrate Metal Recovery
% Cu % Ni
Maturi Bulk #1 93.7 96.1
Maturi Bulk #2
Maturi Ni-Cu 91.2 97.6
Recovery of Precious Metals from CESL™ residue
Precious metals including gold, platinum and palladium remain in residue
throughout the leaching process and are recovered from the residue via
flotation. A weighted precious metals recovery from the leach residue of
90.9%, 82.6%, and 88.1% for Maturi Bulk #1; 88.2%, 52.5%, and 78.8% for Maturi
Bulk #2; and 75.0%, 75.0% and 75.0% for Maturi Ni-Cu was achieved for gold,
platinum, and palladium respectively.
Compositions of the flotation products for each concentrate processed are
presented in Table 2.
Table 2 - Precious Metals Flotation Concentrate Product
S (t) S[o] Au Pt Pd
Concentrate % % g/t g/t g/t
Maturi Bulk #1 85.8 81.4 6.1 11.0 33.0
Maturi Bulk #2 93.8 91.4 4.1 5.3 19.8
Maturi Ni-Cu 97.0 94.6 2.5 6.8 21.4
Although not integrated within the pilot plant flowsheet, bench testwork was
performed to further upgrade the material to elemental sulphur and a separate
Precious Metals cake using sulphur melting. The grade of the Precious Metals
cake for the Maturi nickel-copper concentrate would be approximately 225 g/t
assuming the cake retained an elemental sulphur grade of 45%.
Further metallurgical testing will be conducted during pre-feasibility in
order to optimize the selected process and flowsheet design.
Tom Pugsley, Director of Duluth Metals is the Qualified Person for Duluth
Metals in accordance with NI 43-101 of the Canadian Securities Administrators,
and is responsible for the review of the technical content of this press
About Duluth Metals Limited
Duluth Metals Limited is committed to acquiring, exploring and developing
copper, nickel and platinum group metal (PGM) deposits. Duluth Metals has a
joint venture with Antofagasta plc on the Twin Metals Minnesota Project,
located within the rapidly emerging Duluth Complex mining camp in
north-eastern Minnesota. The Duluth Complex hosts one of the world's largest
undeveloped repositories of copper, nickel and PGMs, including the world's
third largest accumulation of nickel sulphides, and one of the world's largest
accumulations of polymetallic copper and platinum group metals. Aside from the
joint venture, Duluth Metals retains a 100% position on approximately 40,000
acres of mineral interests on exploration properties adjacent to and nearby
the Twin Metals Minnesota LLC joint venture.
About Twin Metals Minnesota LLC
Twin Metals Minnesota, LLC, is a joint venture company, 60 percent owned by
Duluth Metals Limited and 40 percent by Antofagasta plc. Twin Metals was
formed in 2010 to pursue the development and operation of a copper, nickel and
platinum group metals (strategic metals) underground mining project within the
Duluth Complex in northeastern Minnesota. Twin Metals holds mineral and land
assets of approximately 32,000 acres of leased and permitted land, including
mineral resources prepared in compliance with the requirements of NI 43-101.
This press release contains forward-looking statements (including
"forward-looking information" within the meaning of applicable Canadian
securities legislation and "forward-looking statements" within the meaning of
the US Private Securities Litigation Reform Act of 1995) relating to, among
other things, the results of drilling operations of Duluth Metals and
exploration and mine development. Generally, forward-looking statements can
be identified by the use of words such as "plans", "expects" or "does not
expect", "is expected", "budget", "scheduled", "estimates", "forecasts",
"intends", "anticipates" or "does not anticipate", or "believes", or
variations of such words and phrases or statements that certain actions,
events or results "may", "could", "would", "might" or "will be taken", "occur"
or "be achieved". Duluth Metals has relied on a number of assumptions and
estimates in making such forward-looking statements, including, without
limitation, the prices of copper, nickel and platinum group metals (PGMs) and
the costs associated with continuing exploration and mining development.
Such assumptions and estimates are made in light of the trends and conditions
that are considered to be relevant and reasonable based on information
available and the circumstances existing at this time. A number of risk
factors may cause actual results, level of activity, performance or outcomes
of such exploration and/or mine development to be materially different from
those expressed or implied by such forward-looking statements including,
without limitation, whether such discoveries will result in commercially
viable quantities of such mineralized materials, the possibility of changes to
project parameters as plans continue to be refined, the ability to execute
planned exploration and future drilling programs, possible variations of
copper, nickel and PGM grade or recovery rates, the need for additional
funding to continue exploration efforts, changes in general economic, market
and business conditions, and those other risks set forth in Duluth Metals'
most recent annual information form under the heading "Risk Factors" and in
its other public filings. Statements related to "reserves" and "resources"
are deemed forward-looking statements as they involve the implied assessment,
based on realistically assumed and justifiable technical and economic
conditions, that an inventory of mineralization will become economically
extractable. Forward-looking statements are not guarantees of future
performance and such information is inherently subject to known and unknown
risks, uncertainties and other factors that are difficult to predict and may
be beyond the control of Duluth Metals. Although Duluth Metals has attempted
to identify important risks and factors that could cause actual actions,
events or results to differ materially from those described in forward-looking
statements, there may be other factors and risks that cause actions, events or
results not to be as anticipated, estimated or intended. Consequently, undue
reliance should not be placed on such forward-looking statements. In addition,
all forward-looking statements in this press release are given as of the date
hereof. Duluth Metals disclaims any intention or obligation to update or
revise any forward-looking statements, whether as a result of new information,
future events or otherwise, save and except as may be required by applicable
securities laws. The forward-looking statements contained herein are
expressly qualified by this disclaimer.
For further information:Mara Strazdins Vice President Investor Relations and
Corporate Communications Telephone: +1-416-369-1500 ext. 222 Email:
email@example.com Webpage: http://www.duluthmetals.com Vern Baker
President Telephone: +1-651-389-9990 Email: firstname.lastname@example.org
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