Argonaut Gold Inc. Reports on Metallurgical Test Work for El Castillo Sulphide
28 November 2011 - 2:20PM
Marketwired Canada
Argonaut Gold Inc. (TSX:AR) ("Argonaut Gold", "Argonaut" or the "Company")
announces initial results regarding possible heap leaching of El Castillo
sulphides. SRK's November 6, 2011 technical report includes a measured and
indicated ("M&I") sulphide resource of 1.5 million ounces at an average grade of
0.32 g/t (please see foot note #1) which underlies oxide and transitional gold
mineralization at El Castillo.
It is important to note, that the sulphide material will not be accessed for
several years as we continue to mine the oxide and transition ores. However,
given the large size of these resources, the company has completed preliminary
metallurgical testing.
To view "Map #1", please visit the following link:
http://media3.marketwire.com/docs/argonaut_gold_nov28_map01.pdf
In regards to the results generated to date, Peter Dougherty, President and CEO
for Argonaut Gold said "Column tests conducted in early 2011 confirmed that the
leach cycle was very rapid with over 90% of the leachable metal recovered in the
first 10 days. This, coupled with low reagent consumption, supports the
possibility that sulphides can be leached."
Mr. Dougherty added "However, within the El Castillo deposit there is
significant variability to how sulphides react to cyanide leaching. The Company
is currently reviewing known variables within the deposit that could influence
recoveries. These include host rock, sulphide content and fragmentation.
Additional metallurgical testing and characterization studies will need to be
completed."
Historical Metallurgical Test Work
In May 2009, Castle Gold Corp. performed preliminary metallurgical test work
with SGS Mineral Services Lakefield, Ontario Canada (coarse ore cyanide bottle
roll testing) on the sulphides indicating recoveries from as high as 42.8% for
one sample to as low as 8.3% (3/4 inch to 1/4 inch crush sizes for 21 days
leaching). Potential for resource growth and adjustments to the future
production profile at El Castillo prompted further metallurgical work on the
sulphides. (See press release May 7, 2009).
Recent Metallurgical Work
In the fall of 2010 the company completed 7 core holes within key mineralized
areas of the sulphide deposit. This material was shipped to Kappes Cassiday
Associates ("KCA") in Reno, Nevada for metallurgical testing. Their work
included 96 hour bottle roll tests on sulphide material with an average head
grade of .501 g/t gold resulting in an average gold extraction of 53%.
Their column test work reported gold recoveries of between 26% and 51% with an
average of 38%. The column tests ran for 60 days on -3/8 inches (9.5 mm)
particle sizing in four separate columns.
----------------------------------------------------------------------------
Consumption Consumption
Column Test Head Assay g/t Au Extraction % Au Cyanide kg/MT Lime kg/MT
----------------------------------------------------------------------------
DCA - 1 0.264 26% 1.04 2.0
----------------------------------------------------------------------------
DCA - 2 0.618 34% 1.53 3.5
----------------------------------------------------------------------------
DCA - 4 0.606 39% 1.20 2.5
----------------------------------------------------------------------------
DCA - 5 0.328 51% 0.92 2.0
----------------------------------------------------------------------------
These findings support the potential for leach application of the sulphide ore.
Based upon KCA's experience with mostly clean non-reactive ores, cyanide
consumption in production heaps would be only 25-33% of the laboratory column
test consumptions. Additionally, it was found that extraction was quite rapid
with over 75% of the leachable gold reporting to solution in the first 15 days
of leaching.
To view "Map #2", please visit the following link:
http://media3.marketwire.com/docs/argonaut_gold_nov28_map02.pdf
In the spring of 2011 the company completed an additional 16 core holes for
further metallurgical testing of the sulphides. (Please refer to map #2). These
holes were positioned to intersect sulphide zones that underlie the final
oxide/transition pit areas. Sulphide composites were compiled from three main
areas referred to as the North, Central (or main) and South zones. These
composites were again sent to KCA in Reno who completed bottle roll and column
tests.
The findings:
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Bottle Roll Test Calculated Head gms Au/MT Extraction % Au Time
----------------------------------------------------------------------------
North 0.814 78% 96 hours
----------------------------------------------------------------------------
Central (main) 0.066-0.441 21%-51% 48 hours
----------------------------------------------------------------------------
South 0.214 58% 96 hours
----------------------------------------------------------------------------
The cyanide bottle roll tests reported gold recoveries between 21%-78%. KCA also
completed column tests on composites representative of the three study areas.
Results are noted in the following table:
----------------------------------------------------------------------------
Head Assay Extraction % Consumption Consumption # Days under
Column Test g/t Au Au Cyanide kg/MT Lime kg/MT Leach
----------------------------------------------------------------------------
North
composite 0.92 48% 0.75 2.11 72
----------------------------------------------------------------------------
Central 0.075 -
(Main) 0.442 11% - 35% 0.50 - 0.80 3.01 - 3.09 40
----------------------------------------------------------------------------
South
composite 0.29 39% 0.67 2.24 72
----------------------------------------------------------------------------
Column test work showed a wide range of recovery from 11% to 48%. Recovery was
rapid with 90% of the metal recovered in the first 10 days of leaching. Sulphide
tests have provided mixed results and the Company will complete additional
testing to further define the metallurgical variability of the sulphide zones
and their possible economic significance.
Technical Information and Mineral Properties Reports
The technical information contained in this document has been prepared under
supervision by Mr. Thomas H. Burkhart, Argonaut's Vice President of Exploration,
and a qualified person as defined by NI 43-101.
Information on the Company's properties please see the reports as listed below
on the Company's website or on www.sedar.com:
El Castillo Mine NI 43-101 Technical Report on Resources and Reserves,
Argonaut Gold Inc., El Castillo Mine, Durango State,
Mexico dated November 6, 2010
Footnote #1
----------------------------------------------------------------------------
Castillo Sulphide (Global) Measured 70,600 0.328 744,800
----------------------------------------------------------------------------
Castillo Sulphide (Global) Indicated 91,200 0.272 797,500
----------------------------------------------------------------------------
Total Castillo Sulphide (Global) M&I 161,800,000 0.296 1,540,000
----------------------------------------------------------------------------
About Argonaut Gold
Argonaut is a Canadian gold company engaged in exploration, mine development and
production activities. Its primary assets are the production-stage El Castillo
Mine in the State of Durango, Mexico, the development stage and past producing
La Colorada project, the advanced exploration San Antonio project, and several
exploration stage projects, all of which are located in Mexico.
Creating Value Beyond Gold
Cautionary Note Regarding Forward-looking Statements
This news release contains forward-looking statements that involve risks and
uncertainties that could cause results to differ materially from management's
current expectations. Actual results may differ materially due to a number of
factors. Except as required by law, Argonaut Gold Inc. assumes no obligation to
update the forward-looking information contained in this news release.
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