Continental Gold Achieves 95.4% Gold Recoveries from Metallurgical Test Work for the Buriticá Project
April 11 2013 - 5:30AM
Marketwired Canada
Continental Gold Limited ("Continental" or the "Company") (TSX:CNL)(OTCQX:CGOOF)
is pleased to announce metallurgical results for the Buritica project located in
Antioquia, Colombia. Metallurgical test work was performed by McClelland
Laboratories, Inc. of Sparks, Nevada under the supervision of the Company and M3
Engineering of Tucson, Arizona.
Highlights
-- Gravity concentration followed by cyanidation of gravity tails has been
selected as the preferred recovery process for the Buritica project and
will be incorporated in the pre-feasibility study being done by M3
Engineering scheduled for completion in 2014.
-- Gravity concentration followed by cyanidation of gravity tails on all
four 150 kilogram samples submitted for test work yielded overall
metallurgical recoveries of 95.4% and 48.6% for gold and silver,
respectively.
-- A large proportion of the gold can be extracted using gravity separation
with an average recovery rate of 73.8%. This recovery rate was achieved
with a grind size of 80% passing 75 microns.
-- High gold recovery rates were also achieved in the two other processing
routes tested, namely gravity concentration followed by flotation and
leaching of the concentrate and gravity concentration followed by Carbon
In Leach ("CIL").
-- Gravity concentration followed by cyanidation of gravity tails was
selected versus the other processing routes for the Buritica project, as
it will require the smallest area of land with potential for lower
capital costs due to high recovery rates, circuit simplicity and lower
re-agent consumption.
-- One of the composites tested was purposely selected to include high
deleterious elements in order to understand the possible effects on
recoveries. Metallurgical recoveries were not affected. Gold and silver
recoveries for this composite were between 87.6% and 93.9% and between
38.9% and 54.4%, respectively.
Mark Moseley-Williams, President and Chief Operating Officer, commented, "The
cyanidation of gravity tails process achieved consistently high gold recoveries
for all of the composites tested. The process is inherently simpler than the
flotation route. All of the tailings will be filtered for dry stacking, so
environmental management will be readily manageable within acceptable
parameters."
Ari Sussman, CEO, said, "We continue to de-risk Buritica in a methodical fashion
and well within our budget and timeline. Our engineering and metallurgical teams
have done an excellent job advancing our processing to this critical juncture."
Details
Metallurgical testing was conducted on four samples weighing approximately 150
kilograms each from the Buritica project. The sample names and head grades are
as follows:
----------------------------
Head Assay on Composite
Sample
Summary of Results
----------------------------
Assays (g/t)
----------------------------
Sample ID Au Ag
----------------------------
BUMM-001 30.7 39.9
BUMM-002 10.2 47.0
BUMM-003 13.1 38.2
BUMM-004 17.5 33.0
----------------------------
Sample Descriptions:
1. BUMM-001:
This composite was assembled using 52 intervals from drill-holes in the
Yaragua system. This sample represents a reasonable distribution in
strike and depth of the mineralized zones in the different veins present
in the Yaragua system.
2. BUMM-002:
This composite was assembled using 67 intervals from drill-holes in the
Veta Sur system. This sample represents a reasonable distribution in
strike and depth of the mineralized zones in the different veins present
in the Veta Sur system.
3. BUMM-003:
This composite was assembled using 55 intervals from drill-holes in the
Yaragua and Veta Sur systems. Approximately 72% of the samples were from
Yaragua and 28% of the samples were from Veta Sur. This distribution is
consistent with the updated mineral resource estimate, prepared in
accordance with National Instrument 43-101, published in October 2012.
4. BUMM-004:
This composite was assembled using 60 intervals from drill-holes in the
Yaragua and Veta Sur systems. The focus of this composite was to use
samples with abnormally high arsenic values to determine the possible
impact of deleterious elements in gold and silver recoveries. This type
of composite represents a small portion of the overall deposit, and in a
production scenario, would be blended with significantly less
deleterious material.
The metallurgical work performed on the samples included:
1. Gravity concentration followed by flotation on the gravity tails,
followed by leaching of the concentrate ("GFL"). The flotation tests
were conducted at three different grind sizes of approximately 80%
passing 105 microns, 80% passing 150 microns and 80% passing 212
microns. The results indicate that optimal recoveries are obtained at
80% passing 150 microns.
2. Gravity concentration followed by cyanidation of the gravity tails
("GC"). These tests were conducted on each sample at approximately 80%
passing 75 microns using a laboratory Nelson concentrator. The gravity
tail was subjected to a 24-hour agitated cyanidation leach.
3. Gravity concentration followed by CIL on the gravity tails ("GCIL").
These tests were conducted on each sample at approximately 80% passing
75 microns using a laboratory Nelson concentrator. The gravity tail was
subjected to a 72-hour CIL process.
The results of these metallurgical tests are as follows:
----------------------------------------------------------------------------
Gold Recovery
----------------------------------------------------------------------------
Test Work BUMM-01 BUMM-02 BUMM-03 BUMM-04 Average SD Rel %
----------------------------------------------------------------------------
GFL 94.8 87.7 89.6 87.6 89.9 3.76
GC 97.3 95.3 95.7 93.3 95.4 1.74
GCIL 97.6 96.2 96.1 93.9 95.9 1.62
----------------------------------------------------------------------------
----------------------------------------------------------------------------
Silver Recovery
----------------------------------------------------------------------------
Test Work BUMM-01 BUMM-02 BUMM-03 BUMM-04 Average SD Rel %
----------------------------------------------------------------------------
GFL 51.4 40.7 57.2 45.9 48.8 14.5
GC 69.2 30.5 55.7 38.9 48.6 35.6
GCIL 78.6 58.3 67.4 54.4 64.7 16.7
----------------------------------------------------------------------------
Although all of the results of the three tests are extremely similar, the
cyanidation circuit provides a simpler circuit with less equipment that should
be easier to operate and maintain. Carbon in leach (CIL) was not selected
because of the high silver to gold ratios and the presence of other soluble
metals in cyanide leach solutions. Thus, the benefits of lower capital cost and
small area requirements of CIL over CCD plus zinc precipitation were minimized
due to the necessity of having to filter all tailings for secure storage
disposal. It is for these reasons M3 Engineering has recommended to proceed with
variability test work on the gravity concentration followed by cyanidation of
the gravity tails circuit.
Technical Information
The results of the Company's metallurgical testing program and this news release
have been reviewed, verified and compiled by Mark Moseley-Williams, President
and Chief Operating Officer of the Company and a qualified person for the
purpose of National Instrument 43-101. Mr. Moseley-Williams is a mining engineer
with over 17 years' experience in mine construction, expansion projects and
operations in the Americas.
About Continental Gold
Continental Gold Limited is an advanced-stage exploration and development
company with an extensive portfolio of 100%-owned gold projects in Colombia.
Spearheaded by a team with over 40 years of exploration and mining experience in
Colombia, the Company is focused on advancing its high-grade Buritica gold
project to production. On October 1, 2012, the Company announced an updated
mineral resource estimate for the Buritica project prepared in accordance with
NI 43-101 which covers two major vein systems, with combined Measured and
Indicated mineral resource of 3,740,000 tonnes of mineralized material
containing 1,640,000 ounces of gold grading 13.6 g/t gold, 4,600,000 ounces of
silver grading 38 g/t silver, and 55,800,000 pounds of zinc grading 0.7% zinc.
The combined Inferred mineral resource is 13,330,000 tonnes of mineralized
material containing 3,760,000 ounces of gold grading 8.8 g/t gold, 14,200,000
ounces of silver grading 33 g/t silver and 156,500,000 pounds of zinc grading
0.5% zinc. For additional technical information on the Buritica project, please
refer to the technical report entitled "2012 Mineral Resource Estimate of the
Buritica Gold Project, Colombia", dated November 15, 2012 with an effective date
of October 22, 2012, prepared by Mining Associates Pty Limited, available on
SEDAR at www.sedar.com, on the OTCQX at www.otcmarkets.com and on the Company
website at www.continentalgold.com.
In August 2012, Continental achieved an important milestone, receiving formal
approval for the modification of its existing Environmental Impact Assessment.
The amendment allows the Company to build a six-kilometre switchback road and
begin underground development by constructing a one-kilometre access tunnel.
With a goal of being the newest hard rock gold producer in Colombia, Continental
has commenced the construction of the access tunnel, which will initially
provide access for underground drilling and eventually used for commercial
production. A Phase IV drill program is underway at the Buritica project to
further delineate the mineral resource and drill new target zones identified
within its concessions.
An animation video providing an overview of the Buritica project and the
exploration potential is available in the following link: http://bit.ly/Z6HBh9.
Please note that any future production decision will be based on the positive
outcome of a pre-feasibility study in 2014.
Additional details on the Buritica project and the rest of Continental's suite
of gold exploration properties are available at www.continentalgold.com.
Forward-Looking Statements
This press release contains or refers to forward-looking information under
Canadian securities legislation, including statements regarding the estimation
of mineral resources, exploration results, potential mineralization, exploration
and mine development plans, and timing of the commencement of operations, and is
based on current expectations that involve a number of business risks and
uncertainties. Forward-looking statements are subject to significant risks and
uncertainties, and other factors that could cause actual results to differ
materially from expected results. Readers should not place undue reliance on
forward-looking statements. Factors that could cause actual results to differ
materially from any forward-looking statement include, but are not limited to,
failure to convert estimated mineral resources to reserves, capital and
operating costs varying significantly from estimates, the preliminary nature of
metallurgical test results, delays in obtaining or failures to obtain required
governmental, environmental or other project approvals, political risks,
uncertainties relating to the availability and costs of financing needed in the
future, changes in equity markets, inflation, changes in exchange rates,
fluctuations in commodity prices, delays in the development of projects and the
other risks involved in the mineral exploration and development industry
forward-looking statements are subject to significant risks and uncertainties,
and other factors that could cause actual results to differ materially from
expected results. Readers should not place undue reliance on forward-looking
statements. These forward-looking statements are made as of the date hereof and
the Company assumes no responsibility to update them or revise them to reflect
new events or circumstances other than as required by law.
Differences in Reporting of Resource Estimates
This press release was prepared in accordance with Canadian standards, which
differ in some respects from United States standards. In particular, and without
limiting the generality of the foregoing, the terms "inferred mineral
resources," "indicated mineral resources," "measured mineral resources" and
"mineral resources" used or referenced in this press release are Canadian mining
terms as defined in accordance with National Instrument 43-101 - Standards of
Disclosure for Mineral Projects under the guidelines set out in the Canadian
Institute of Mining, Metallurgy and Petroleum (the "CIM") Standards on Mineral
Resources and Mineral Reserves (the "CIM Standards"). The CIM Standards differ
significantly from standards in the United States. While the terms "mineral
resource," "measured mineral resources," "indicated mineral resources," and
"inferred mineral resources" are recognized and required by Canadian
regulations, they are not defined terms under standards in the United States.
"Inferred mineral resources" have a great amount of uncertainty as to their
existence, and great uncertainty as to their economic and legal feasibility. It
cannot be assumed that all or any part of an inferred mineral resource will ever
be upgraded to a higher category. Under Canadian securities laws, estimates of
inferred mineral resources may not form the basis of feasibility or other
economic studies. Readers are cautioned not to assume that all or any part of
measured or indicated mineral resources will ever be converted into reserves.
Readers are also cautioned not to assume that all or any part of an inferred
mineral resource exists, or is economically or legally mineable. Disclosure of
"contained ounces" in a resource is permitted disclosure under Canadian
regulations; however, United States companies are only permitted to report
mineralization that does not constitute "reserves" by standards in the United
States as in place tonnage and grade without reference to unit measures.
Accordingly, information regarding resources contained or referenced in this
press release containing descriptions of our mineral deposits may not be
comparable to similar information made public by United States companies.
FOR FURTHER INFORMATION PLEASE CONTACT:
Continental Gold Limited
Nisha Hasan
Director, Investor Relations
+1.416.583.5611
info@continentalgold.com
www.continentalgold.com
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