07/01/13-10/31/13 | $1,325.31 |
01/01/13-06/14/13 | $1,543.17 |
07/01/12-12/14/12 | $1,687.83 |
01/01/12-06/30/12 | $1,656.81 |
11/08/11-12/14/11 | $1,721.19 |
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 ofDecember 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.
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
Table 1 - 2011 Gravity Test Results ---------------------------------------------------------------------------- Product Mass, % Grade, g/t Recovery, % ------------------------------------------------ Au Pt Pd Au Pt Pd ---------------------------------------------------------------------------- C2 Concentrate 1.5 840.5 18.2 26.9 79.5 6.3 6.9 ---------------------------------------------------------------------------- C3 Concentrate 1.4 697.2 1.7 7.9 76.6 2.7 7.1 ----------------------------------------------------------------------------
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
The grade of the gravity tailings composite is given in Table 2 below:
Table 2 - Gravity Tailings Composite Feed Grade --------------------------------------------------------------- Element Pt Pd Au --------------------------------------------------------------- Grade, ppm 2.0 3.4 1.9 ---------------------------------------------------------------
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 ---------------------------------------------------------------------------- Major Components Au (g/t) Pt (g/t) Pd (g/t) Ag (g/t) C (%) ---------------------------------------------------------------------------- Grade 6.6 7.9 10.4 6.5 15.7 ----------------------------------------------------------------------------
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 (
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 ---------------------------------------------------------------------------- Leach Conditions Wt % solids Au Rec (%), 12 hrs ---------------------------------------------------------------------------- 2% NaCN 25 98.8 ---------------------------------------------------------------------------- 2% NaCN + Kero 25 99.2 ---------------------------------------------------------------------------- 1% NaCN 25 99.2 ---------------------------------------------------------------------------- 2% NaCN 20 99.3 ----------------------------------------------------------------------------
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
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.
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,
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 (
FOR FURTHER INFORMATION PLEASE CONTACT:Colossus Minerals Inc. Ann Wilkinson Vice-President, Investor Relations (416) 643-7655 awilkinson@colossusminerals.com www.colossusminerals.com Source:Colossus Minerals Inc.