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.
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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
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DCA - 2 0.618 34% 1.53 3.5
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DCA - 4 0.606 39% 1.20 2.5
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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
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Castillo Sulphide (Global) Measured 70,600 0.328 744,800
----------------------------------------------------------------------------
Castillo Sulphide (Global) Indicated 91,200 0.272 797,500
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Total Castillo Sulphide (Global) M&I 161,800,000 0.296 1,540,000
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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.
Contacts: Argonaut Gold Inc. Nichole Cowles Investor Relations
Manager (775) 284-4422 x
101nichole.cowles@argonautgoldinc.comwww.argonautgoldinc.com
Argonaut Gold (TSX:AR)
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