Colossus Minerals Announces Significant Achievement in Metallurgical Recoveries of Platinum Group Metals From Serra Pelada
TORONTO, ONTARIO -- (Marketwire) -- 04/10/12 -- Colossus Minerals Inc. (the "Company" or "Colossus") (TSX: CSI)(OTCQX: COLUF) is pleased to provide an update on the metallurgical test-work conducted on samples from Colossus' 75% owned Serra Pelada Gold-Platinum-Palladium Project. The Serra Pelada Project is a Colossus-COOMIGASP Joint Venture located in Para, Brazil.
All test work was conducted on samples from drill hole SPD-113 (74.40 metres at 31.17 g/t gold, 3.02 g/t platinum and 6.78 g/t palladium - please refer to news release of September 7, 2011), an interval with relatively low platinum group metals ("PGM") grades compared with other assay results previously disclosed.
Highlights
-- Previously disclosed gravity test-work achieved recovery rates for gold
between 77% and 88%, with recoveries from SPD-113 ranging between 77%
and 80% (please refer to news release of December 5, 2011), with
indicated platinum and palladium recoveries as presented in detail
below.
-- Flotation testing of the composite gravity tails sample achieved
recovery rates of 77%, 78%, and 69% for the remaining gold, platinum and
palladium respectively.
-- The significant metallurgical flotation achievement for PGM's uses a
readily available, conventional and low cost combination of reagents.
-- The flotation concentrate was produced after only six minutes of
flotation and is free of deleterious elements.
-- Based on all metallurgical results achieved to date, Colossus expects
that a combined gravity and flotation process in a plant should recover
between 92%-96% gold, 74%-78% platinum and 67%-71% palladium.
Claudio Mancuso, President & Chief Executive Officer commented, "The metallurgical recoveries for PGM's have exceeded our expectations, especially given that drill hole SPD-113 exhibits lower PGM grades than other drill holes at Serra Pelada. More importantly, the PGM's were recovered using a simple flotation process and conventional flotation reagents, which resulted in a much quicker than expected flotation time." Mr. Mancuso further commented, "I would like to thank Andy Holloway, his team at AGP Mining Consultants Inc. and the team at Blue Coast Research Ltd. for their tireless efforts on the PGM process work. Their commitment to the project has led to these particularly encouraging results."
Update on Metallurgical Testwork on CMZ Composite Material
1. Gravity Program
Gravity concentration testwork completed in late 2011 confirmed the amenability of Central Mineralized Zone (CMZ) samples to a simple gravity gold separation process. Multi-stage gravity separation tests conducted at Met-Solve Laboratories (Langley, BC) on two composite samples from SPD-113 (drilled on section 00 of the CMZ) confirmed previous test results, with gravity recoverable gold values of 76.6% and 79.5%. Grades and recoveries are summarized in Table 1 below:
Table 1 - 2011 Gravity Test Results
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Product Mass, % Grade, g/t Recovery, %
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Au Pt Pd Au Pt Pd
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C2 Concentrate 1.5 840.5 18.2 26.9 79.5 6.3 6.9
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C3 Concentrate 1.4 697.2 1.7 7.9 76.6 2.7 7.1
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Despite excellent results for gold, as expected, the very fine-grained platinum and palladium minerals at Serra Pelada do not recover well in a gravity-only process and therefore recent efforts have focused on froth flotation of the gravity circuit tailings as a means to recover platinum, palladium and residual gold.
Repeat gravity concentration tests were therefore completed on SPD-113 composites to provide samples of gravity tailings and gravity concentrate, suitable for downstream flotation and intensive cyanidation testwork.
2. Flotation Program
The ongoing program of PGM flotation testing, conducted at Blue Coast Research Ltd. (Nanaimo, BC), has made excellent progress, with a recent breakthrough in PGM recovery rates helping to achieve improved results. Over thirty flotation tests have been conducted on a blend of tailings from the C2/C3 gravity program discussed above, and these have examined various separation strategies and combinations of reagents.
The grade of the gravity tailings composite is given in Table 2 below:
Table 2 - Gravity Tailings Composite Feed Grade
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Element Pt Pd Au
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Grade, ppm 2.0 3.4 1.9
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Of note, despite the relatively low PGM grades in this composite sample, flotation test SP-F23, achieved gold, platinum and palladium recoveries of 76.8%, 77.6% and 68.7% respectively into a clean, low grade rougher concentrate after only six minutes of flotation. This was achieved using conventional methods and a straightforward combination of reagents. Figure 1 below is a plot of PGM (Pt + Pd) and gold recovery versus time, and illustrates the improvement in flotation recovery rates compared with previous work. The superior performance noted in SP-F23 has been replicated in nine subsequent tests.
To view Figure 1, please visit the following link: http://media3.marketwire.com/docs/csi410f1.pdf.
A clean, low grade PGM concentrate is the product of this improved flotation process. Concentrate grades at this point of the process are given in Table 3 below. Concentrations of deleterious elements such as arsenic, bismuth, cadmium, chromium and magnesium oxide are very low and uniformly below penalty thresholds. A notable feature is the relatively high concentration of carbon (graphite) which will be reduced substantially by the removal of carbon known to result from a simple calcining step. Ongoing test-work to clean rougher concentrates is also expected to result in further improvements in the PGM grade versus recovery relationship.
Table 3 - Rougher Flotation Concentrate Analysis
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Major Components Au (g/t) Pt (g/t) Pd (g/t) Ag (g/t) C (%)
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Grade 6.6 7.9 10.4 6.5 15.7
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Although average "as mined" grades will be more clearly defined through the planned underground drilling and bulk sampling program, the froth flotation process defined by Blue Coast is expected to benefit greatly from higher PGM head grades than the 7.3 g/t combined Au+Pt+Pd tested in SP-F23. As flotation circuit feed grades increase, so the concentrate grades are expected to rise proportionally while maintaining similar recovery rates.
As the metallurgical program continues, efforts will focus on the following priorities:
-- Confirm that calcination of flotation concentrates will remove the
majority of carbon (currently assaying 15.7% in the rougher
concentrate).
-- Further refine process conditions to improve PGM flotation concentrate
grade and/or recovery.
-- Confirm the current flotation results on a range of variability samples,
including higher grade composites.
-- Test the amenability of the carbon-rich PGM flotation concentrate to DC
Arc Furnace technology.
3. Cyanidation Program
A program of intensive cyanidation and electrowinning testing has been completed at Gekko Systems (Australia) and has demonstrated the amenability of Serra Pelada gravity concentrates to this modern and efficient gold processing stage.
Samples of gravity concentrate from the 2011 Met-Solve gravity program were blended to produce a Master Composite, suitable for leaching by cyanidation. The intensive leach results are given in Table 4 below:
Table 4 - Intensive Leach Results
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Leach Conditions Wt % solids Au Rec (%), 12 hrs
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2% NaCN 25 98.8
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2% NaCN + Kero 25 99.2
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1% NaCN 25 99.2
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2% NaCN 20 99.3
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These results are very encouraging, and demonstrate that the presence of carbon in the gravity concentrates has no negative "preg-robbing" impact on the extraction process. The pregnant leach solutions resulting from this cyanidation work have been tested for amenability to electrowinning and have been found to be suitable for this final upgrading stage.
Taken together with the previous gravity testwork, this indicates that overall gravity plus flotation process recoveries of 92-96% gold, 74-78% platinum and 67-71% palladium should be achievable.
4. Engineering and Construction
In connection with the engineering and construction of the processing facility, the Company announces it has engaged the services of DRA Americas Inc. of Toronto (DRAA), recognized specialists in the design and construction of PGM mineral processing plants. DRAA is part of a global group which employs some 3,000 people through projects and operations in Africa, Australia, China, India, Europe and the Americas. They were selected as a result of their experience in PGM processing, and a 25-year track record of bringing projects in on schedule and under budget.
Engineering for the first phase, gravity processing plant has commenced and construction is anticipated to be complete early in the first quarter of 2013. Orders for long lead-time items in the process plant, including the intensive leach reactors, electrowinning cells, the gravity concentrators and the ore scrubber have been have been placed and are scheduled to be delivered during the third quarter of 2012. Preliminary engineering and cost estimating for a flotation, dewatering and calcination process will begin later in 2012.
Andy Holloway, P.Eng, Principal Process Engineer at AGP Mining Consultants, is a qualified person under National Instrument 43-101 and is responsible for the Company's metallurgical program and results and has verified the related content disclosed herein.
About Colossus:
Colossus is a development-stage mining company focused on bringing its Serra Pelada project into production. Serra Pelada, located in the mineral prolific Carajas region in the State of Para, Brazil, is host to one of the highest grade gold and platinum group metals deposits in the world. Between 1980 and 1986 Serra Pelada was host to the largest precious metals rush in Latin American history. Coverage of this famous mining rush by 60 Minutes can be viewed by following the link below. Colossus Minerals shares, warrants and notes trade on the Toronto Stock Exchange (TSX) under the symbols CSI, CSI.WT.A and CSI.NT respectively and in the United States its Common Shares trade on the OTCQX under the symbol COLUF. The Company is headquartered in Toronto, Canada.
http://video.au.msn.com/watch/video/the-treasure-of-serra-pelada/xx3k2px
CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING INFORMATION
Forward-looking statements in this press release include statements regarding the timing and nature of future exploration and development programs that are dependent on projections that may change as drilling continues, or if unexpected ground conditions are encountered. The Company does not currently have any mineral properties that are in production or that contain a reserve as defined by National Instrument 43-101. In addition, areas of exploration potential are identified which will require additional drilling to determine whether or not they contain similar mineralization to areas that have been explored in more detail. Significant additional drilling is required at Serra Pelada to fully understand system size.
Except for statements of historical fact relating to Colossus, certain statements in this press release relating but not limited to the Company's exploration and development plans, activities and intentions, constitute "forward-looking information" within the meaning of the Securities Act (Ontario) or "forward-looking statements" within the meaning of the United States Private Litigation Reform Act of 1995. These forward-looking statements represent management's best judgment based on current facts and assumptions that management considers reasonable. Forward-looking statements are frequently characterized by words such as "target", "plan", "expect", "project", "intend", believe", "anticipate" and other similar words, or statements that certain events or conditions "appear to", "may" or "will" occur. Forward-looking statements are based on the opinions and estimates of management at the date the statements are made, and are subject to a variety of risks and uncertainties and other factors that could cause actual events or results to differ materially from those projected in the forward-looking statements. The factors include but are not limited to risks related to the joint venture operation, actual results of exploration activities, the inherent risks involved in the exploration and development of mineral properties, changes in project parameters as plans continue to be refined, delays in obtaining government approvals, the uncertainties of project cost overruns or unanticipated costs and expenses, uncertainties relating to the availability and costs of financing needed in the future, the uncertainties inherent to conducting business in Brazil and the rest of Latin America, the availability of equipment and supplies, unexpected adverse climate conditions, the reliance on only a few key members of management, as well as those factors discussed in the section entitled "Risk Factors" in the Company's most recent Annual Information Form filed with Canadian provincial securities regulatory authorities and other regulatory filings which are posted on SEDAR at www.sedar.com. Unless required by law, Colossus undertakes no obligation to update forward-looking statements if circumstances or management's estimates or opinions should change. The reader is cautioned not to place undue reliance on forward-looking statements.
Contacts:
Colossus Minerals Inc.
Ann Wilkinson
Vice-President, Investor Relations
(416) 643-7655
awilkinson@colossusminerals.com
www.colossusminerals.com