Continental Gold Achieves 95.4% Gold Recoveries from Metallurgical Test Work for the Buriticá Project
TORONTO, ONTARIO -- (Marketwired) -- 04/11/13 -- 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:
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Head Assay on Composite
Sample
Summary of Results
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Assays (g/t)
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Sample ID Au Ag
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BUMM-001 30.7 39.9
BUMM-002 10.2 47.0
BUMM-003 13.1 38.2
BUMM-004 17.5 33.0
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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:
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Gold Recovery
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Test Work BUMM-01 BUMM-02 BUMM-03 BUMM-04 Average SD Rel %
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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
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Silver Recovery
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Test Work BUMM-01 BUMM-02 BUMM-03 BUMM-04 Average SD Rel %
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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
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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.
Contacts:
Continental Gold Limited
Nisha Hasan
Director, Investor Relations
+1.416.583.5611
info@continentalgold.com
www.continentalgold.com