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 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 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 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
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 material.
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 cleaning.
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
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
Maturi Bulk #1
Maturi Bulk #2
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.
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 release.
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