- Published: 25 March 2009
- Written by Editor
Greystar Receives Positive Prefeasibility Study for Its Angostura Gold Project
Greystar Resources Ltd. ("Greystar" or the "Company") (TSX:GSL)(AIM:GSL) announces the completion by GRD Minproc Ingenieria y Construccion Ltda. Chile ("Minproc") of a positive Prefeasibility Study ("Study") for its wholly-owned Angostura gold project located in northeastern Colombia.
Conclusions
- Using a base case gold price of $700/oz in the first three years of operation and $650/oz thereafter, the Study envisions average annual production of 511,000 ounces of gold and 2.3 million ounces of silver over a 15 year mine life;
- Base case pre-tax after government royalty Net Present Value (NPV) at a 6% discount is $558 million generating an Internal Rate of Return of 19.0%. Using a gold price of $750/oz for the life of mine, the NPV at a 6% discount is $942 million with an Internal Rate of Return of 24.9%;
- The Study entails a 70,000 tonne per day conventional heap leach operation producing a total of 4.2 million ounces of gold over the mine life, plus a 5,200 tonne per day conventional milling and flotation process producing a total of 3.5 million ounces of gold in concentrates over the mine life;
- The average cash operating costs for life of mine (LOM), excluding by-product credits is $391/oz;
- Start-up capital costs are $638 million, with an accuracy of +/- 25% with additional sustaining capital of $307 million including the construction of a concentrator;
- Envisions the start of construction in 2010, with production commencing in 2012.
"This Study involved an in depth analysis of all the aspects of our project, including the evaluation of several different alternatives for both the mining and process streams. The end result is a financially robust model with strong cash flow generation at a conservative gold price," said Mr. Frederick Felder, Executive Vice-President of Greystar. "Based on the positive results of the Study, we will be proceeding with the next phase, which is a bankable feasibility study. This will include the Environmental and the Social Impact Studies and their submissions to the Colombian Ministry of the Environment. Both studies are expected to be completed in the fourth quarter of 2009."
The Study was completed by Minproc to prefeasibility study standards and marks the first stage to completing a bankable feasibility study. The Minproc Study describes the resources, metallurgy, geotechnical study, open pit mine plan, metallurgy process design, operating and capital costs and financial analysis for the Angostura Gold Project. The Minproc Study was prepared based on an updated NI 43-101 resource estimate completed by the Greystar staff and under the overall supervision of consulting company Metalica Consultores S.A. ("Metalica") from Chile, as announced in the Company's news release on December 9, 2008, and which updated NI 43-101 resource estimate is available for review on SEDAR at www.sedar.com. All dollar amounts are in US dollars unless otherwise stated.
Angostura Gold Project Mineral Resources
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CATEGORY
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Measured Indicated Measured + Indicated Inferred
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Kt 148,900 182,006 330,907 90,779
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Au (g/t) 0.8 1.3 1.1 1.2
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Ag (g/t) 4 7 6 6
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Au (koz) 3,736 7,813 11,549 3,472
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Ag (koz) 20,000 41,000 61,000 18,000
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Cut off grades: 0.3 g/t Au for oxides; and 0.45 g/t Au for
sulfides.
Angostura Gold Project Mineral In Pit Resources
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CATEGORY
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Measured Indicated Measured + Indicated Inferred
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Kt 179,240 133,117 312,357 18,216
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Au (g/t) 0.6 1.2 0.9 1.8
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Ag (g/t) 4 7 5 10
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Au (koz) 3,588 4,998 8,586 1,057
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Ag (koz) 21,109 29,618 50,727 6,000
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Note: In-Pit Resources includes Inferred Resources that
represent less than 6 per cent of the Measured and Indicated
Resources by volume.
Angostura Gold Project Mineral Reserves
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Process / Category Proven Probable Total
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kt 174,923 118,563 293,486
Au (g/t) 0.5 0.7 0.6
Heap Leach Ag (g/t) 3 5 4
Au (koz) 2,912 2,551 5,463
Ag (koz) 19,289 18,783 38,071
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kt 4,317 14,554 18,871
Au (g/t) 4.9 5.2 5.1
Flotation Ag (g/t) 13 23 21
Au (koz) 676 2,448 3,123
Ag (koz) 1,820 10,836 12,656
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kt 179,240 133,117 312,357
Au (g/t) 0.6 1.2 0.9
Total Ag (g/t) 4 7 5
Au (koz) 3,588 4,998 8,586
Ag (koz) 21,109 29,618 50,727
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It is anticipated that the Mineral Reserves will increase as inferred resources are converted to reserves, as a result of the inclusion of 55 additional drill holes from infill drilling, comprising 24,574 meters, completed after the cutoff date for the data incorporated in the December Resource study, which was used in the Prefeasibility Study. This drilling was done on 25 meter line centers in order to improve the confidence level of high grade structures.
Mining
The pit design completed by Metalica minimizes waste extraction and results in a mine plan containing 331 million tonnes grading 0.9 g/t gold and 5.3 g/t silver. Total gold and silver production over a 15 year mine life is estimated to be 7.7 million ounces of gold and 34.5 million ounces of silver. The life of mine waste stripping ratio is estimated at 2.25:1.
Conventional open pit mining equipment will be used, a combination of hydraulic shovels (29 cuyd) and wheel loaders (22 cuyd) have been considered, loading off-the-road trucks (190 tonnes). Pit design is based in a 3 dimensional geotechnical model, as product of the geotechnical study carried out by iC Consulenten and reviewed by GeoBlast S.A. A bench height of 6.25 meters has been selected, as a result of the trade-off study by Metalica optimizing the mine operations to minimize the ore dilution by maintaining selectivity, while utilizing an efficiency fleet of the loading and haulage equipment.
Metallurgy and Processing
The Study contemplates using both a conventional heap leach process and a conventional flotation process. The initial start up (scheduled to be 2012) would entail the processing of oxides, transitional and low sulfide material by heap leaching. In year three (scheduled to be 2014) the operation would also start producing flotation sulfide concentrates from higher grade, high sulfur mineralization comprising 22.6 million tonnes grading 5.1 grams gold per tonne for sale to external sources. The oxide, transitional and low sulfide material is optimally treated at a rate of 70,000 tonnes per day and would be processed using a conventional valley-fill heap leach operation with crushing to a nominal 19mm feed size. Oxides and transitional material will be conveyed and stacked by trucks on two heap leach pads; Angostura and Paez. The pregnant leach solutions (PLS) will be treated in a Merrill Crowe process plant for metal production.
Starting in year 3, the primary sulfide material would be treated at a rate of 5,200 tonnes per day with crushing, grinding to a nominal 106 microns feed size, flotation, thickening and filtering for the production of a gold-silver concentrate. The shipping and treatment of the flotation concentrates to a smelter is currently being considered as the economic option by the study, however other more likely options are currently being considered (see 'Moving Forward' section below). Flotation tailings would be dewatered; agglomerated and added to the heap for leaching. Under this scenario, a tailings treatment facility will not be necessary, thereby eliminating a significant cost for the project.
The process flow sheet selection is a consequence of detailed metallurgy studies, where a variety of tests have been carried out on 209 composites made from 9,789 meters of drill core and 26 tonnes of bulk samples. The test work involved 253 bottle roll tests, 88 column leach tests, 133 flotation tests, 21 mineralogy analyses and 59 bio-oxidation tests. The test-work results were used for several trade-off studies by Minproc, in order to define the best combination of process routes for the Angostura mineralization.
The oxide, transitional and low sulfide material have been confirmed to be amenable to simulated heap leaching treatment at 19mm feed size and follow-up testing is currently being initiated to include the evaluation of run-of-mine heap leaching. Meanwhile, the high-sulfide material with high gold values responded well to conventional flotation processing.
Project Highlights
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Production Data
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Life of Mine 15 Years
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Heap Leach Throughput 70,000 tonnes per day
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Heap Leach metallurgical gold recovery 70.6%
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Grinding and Flotation Throughput 5,200 tonnes per day
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Grinding and Flotation metallurgical gold recovery 94%
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Average annual gold production 511,000 Ounces
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Total gold produced 7.7 million Ounces
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Costs
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Total operating costs (excluding by-product credits) $391 per Ounce
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Total operating costs (excluding by product credits) $9.1 per tonne
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Initial Investment $638 million
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Deferred Capital $307 million
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Economics @ $700 (First 3 years) and $650 (Thereafter)
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Net Present Value @ 6%,pre-tax, after government $558 million
Royalty
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Internal rate of return, pre-tax, after government 19.0%
royalty
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"As a consequence of better knowledge about the metallurgy of the deposit, a new recovery model was developed, taking into account the sulfur grade, its associated operating cost and recovery. The pit optimization now shows the high sulfur, low gold grade material being sent to the waste dump, as opposed to the previous studies, where this material was going to the Heap. This is an important de-risk factor incorporated in the present study and is also more cost effective for the project, as the high sulfur being treated in the heap resulted in a loss, due to the high cost of reagents and low recovery," said Luis Arguelles, Greystar's Project Director of Angostura.
Angostura Gold Project - Mine, Processing Plant and Production plans
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Years 0 1 2 3 4 5 6 7 8
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Years 2009 2010 2011 2012 2013 2014 2015 2016 2017
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Ore to Mt 14.4 24.6 25.8 25.6 25.5 25.0 25.3
Heap: Au (g/t) 0.5 0.6 0.6 0.6 0.6 0.6 0.6
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Ore to Mt 1.5 1.4 1.5 1.9 1.9
Flotation Au (g/t) 5.9 5.4 5.6 5.6 5.5
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Total Ore Mt 14.4 24.6 27.1 27.0 27.0 26.9 27.2
to Process Au (g/t) 0.5 0.6 0.9 0.9 0.8 1.0 0.9
Ag (g/t) 5 4 6 7 7 7 5
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Waste Mt 2.7 8.6 33.6 65.4 64.1 63.5 63.5 62.8 61.5
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Total Mt 3.8 10.3 48.1 90.5 91.1 90.4 90.5 89.9 88.7
Movement
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Production Au (koz) 214 377 682 638 592 657 644
Ag (koz) 1,180 1,595 3,214 3,502 3,548 3,589 2,577
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Years 9 10 11 12 13 14 15 16
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Years 2018 2019 2020 2021 2022 2023 2024 2025 Total
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Ore to Mt 24.9 25.0 25.2 23.7 19.5 17.2 6.7 308.0
Heap: Au (g/t) 0.6 0.6 0.6 0.6 0.7 0.7 0.8 0.6
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Ore to Mt 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.2 22.6
Flotation Au (g/t) 6.0 4.3 4.4 4.7 4.8 4.5 4.7 5.1 6.1
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Total Ore Mt 26.8 26.9 27.1 25.6 21.4 19.1 8.6 1.2 330.6
to Process Au (g/t) 1.0 0.8 0.8 0.9 1.0 1.1 1.7 5.5 0.9
Ag (g/t) 4 4 5 6 5 5 6 20 5
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Waste Mt 60.1 53.3 49.0 46.8 48.8 48.6 12.5 744.8
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Total Mt 87.1 80.3 76.1 72.6 70.6 68.6 21.1 1.2 1,080.9
Movement
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Production Au (koz) 659 550 575 578 511 446 346 208 7,677
Ag (koz) 2,337 2,064 2,465 2,680 2,269 1,682 1,104 677 34,484
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Note: Tonnes of re-handling material not shown in this chart
Financial Analysis
The Project has been evaluated on a pre-tax basis but after government royalty. Base case was calculated using a gold price of 700 $/oz for the first three years, and 650 $/oz thereafter.
The Study estimates direct capital costs of $638 million, to be invested until 2012, with an accuracy +/- 25%, including an accuracy provision allowance of $32.9 million and $5.1 million in working capital. An additional $307 million in capital, including the construction of the concentrator and an accuracy provision allowance of $23.7 million. The capital cost estimate excludes losses or gains that may arise from foreign exchange rate variations, cost escalation and other factors. Operating costs are estimated at $9.10 per tonne, or $391 per ounce, excluding silver credits. The Internal Rate of Return is 19% at 6 per cent discount.
Project Sensitivities (NPV values pre-tax, after government royalty)
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Gold Price ($/Oz) 600 Base Case 750
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NPV @ 6% ($million) 294 558 942
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IRR (%) 13.3 19.0 24.9
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Capex change 10% Base Case -10%
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NPV @ 6% ($million) 482 558 634
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IRR (%) 16.5 19.0 21.8
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Operating cost change 10% Base Case -10%
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NPV @ 6% ($million) 387 558 730
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IRR (%) 15.6 19.0 21.9
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Environmental and Social Considerations
Ingetec Ingenieria y Diseno S.A. ("Ingetec"), an independent Colombian firm based in Bogota, undertook the Environmental and Social base line for the project, as well as the hydrology and hydro-geology investigations. This Study addressed all of the requirements established by the Colombian regulations and is to World Bank Group standards. Findings reported include vegetation, animal life, climate and meteorology, air quality, soils, hydrology and water quality. No important issues were reported as impediment for the project development. The archeology study is currently being developed and Greystar has obtained the permit to do this study from the ICAN (Colombian Institute of Archeology).
The social base line study shows that the surrounding communities have a strong commitment to the project, which is not surprising as the area is a historical mining district. Several socialization meetings have been carried out with all the communities directly influenced by the project. There are also no conflicts between Greystar and the small miners in the area of the project.
Greystar has already started the second phase of the Social and Environmental base line, in order to complete the yearly cycle. The second phase is being carried out by the Colombian firm Gradex SA.
It is important to note that Greystar has also obtained the terms of reference for the Environmental Impact Study from the Ministry of Environment.
Moving Forward - Stage II - Feasibility Study
The feasibility study will investigate the possible effect that the current global economic crisis may have impacted the Angostura Project. Gold prices have continued to improve and consensus estimates have risen in recent months. The base case gold price of $700 per ounce for gold for the first three years and $650 per ounce for the rest of the mine life in the Study may be conservative The feasibility study will also look to improve the economics of the project by evaluating:
- The utilization of a fixed primary crusher instead of a semi-mobile, as was defined in the first stage Study;
- The recirculation and concentration of the PLS to optimize the equipment at the Merrill Crowe plant;
- The completion of the run of mine heap leach tests, for which early results indicate that the recovery of gold from oxide and transitional materials is not sensitive to the crush size;
- For the recovery of gold and silver from the flotation concentrates three process streams are being tested for better economic optimization. These are a) roasting the concentrate on site, b) bio-oxidizing the concentrate on site and c) super-fine grinding and tank leaching;
- Testing to evaluate the processing of the lower grade refractory sulfide material using heap bio-oxidation pretreatment followed by heap cyanidation treatment.
Glossary of Key Terms
Contained Ounces, Contained Gold - Represents ounces in the ore before losses during the applicable metallurgical process.
Cut-off Grade - The minimum grade at which a unit of ore will be mined or treated. At the cut-off grade, the value is equal to the costs associated with mining and/or treating the unit of ore.
Dilution - The effect of waste or low-grade material which is unavoidably included in the mined ore, lowering the mining grade.
Grade - The amount of metal in each tonne of ore, expressed as grams per tonne for precious metals (or as troy ounces per short ton in the imperial system), and as a percentage for most other metals.
Heap leaching - A process whereby valuable metals are leached from a heap, or pad, of crushed ore by leaching solutions percolating down through the heap and are collected from a sloping, impermeable liner.
Flotation - A milling process by which some mineral particles are induced to become attached to bubbles of froth and float, and others to sink, so that the valuable minerals are concentrated and separated from the gangue.
Kt - 1,000 X tonnes
Koz - 1,000 X troy ounces
Mineral Resource - A mineral resource is a concentration or occurrence of natural, solid, inorganic or fossilized organic material in or on the Earth's crust in such form and quantity and of such a grade or quality that it has reasonable prospects for economic extraction. The location, quantity, grade, geological characteristics and continuity of a mineral resource are known, estimated or interpreted from specific geological evidence and knowledge. Mineral resources are sub-divided, in order of increasing geological confidence, into inferred, indicated and measured categories.
Inferred Mineral Resources - An inferred mineral resource is that part of a mineral resource for which quantity and grade or quality can be estimated on the basis of geological evidence, limited sampling and reasonably assumed but not verified geological and grade continuity. The estimate is based on limited information and sampling gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drill holes.
Indicated Mineral Resource - An indicated mineral resource is that part of a mineral resource for which quantity, grade or quality, densities, shape and physical characteristics can be estimated with a level of confidence sufficient to allow the appropriate application of technical and economic parameters, to support mine planning and evaluation of the economic viability of the deposit. The estimate is based on detailed and reliable exploration and testing information gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drill holes that are spaced closely enough for geological and grade continuity to be reasonably assumed.
Measured Mineral Resources - A measured mineral resource is that part of a mineral resource for which quantity, grade or quality, densities, shape and physical characteristics are so well established that they can be estimated with confidence sufficient to allow the appropriate application of technical and economic parameters, to support production planning and evaluation of the economic viability of the deposit. The estimate is based on detailed and reliable exploration, sampling and testing information gathered through appropriate techniques from location such as outcrops, trenches, pits, workings and drill holes that are spaced closely enough to confirm both geological and grade continuity.
Mineral resources, which are not mineral reserves, do not have demonstrated economic viability.
Mineral Reserve - The economically mineable part of a Measured or Indicated Mineral Resource demonstrated by at least a Preliminary Feasibility Study. This Study must include adequate information on mining, processing, metallurgical, economic and other relevant factors that demonstrate, at the time of reporting, that economic extraction can be justified. A Mineral Reserve includes diluting materials and allowances for losses that may occur when the material is mined.
Probable Mineral Reserve - The economically mineable part of an Indicated and, in some circumstances, a Measured Mineral Resource demonstrated by at least a Preliminary Feasibility Study. This Study must include adequate information on mining, processing, metallurgical, economic, and other relevant factors that demonstrate, at the time of reporting, that economic extraction can be justified.
Proven Mineral Reserve - Economically mineable part of a Measured Mineral Resource demonstrated by at least a Preliminary Feasibility Study. This Study must include adequate information on mining, processing, metallurgical, economic, and other relevant factors that demonstrate, at the time of reporting, that economic extraction is justified.
Mt - Million tonnes
Stripping/Strip Ratio - The dimensionless ratio of waste to ore in an open pit. Usually expressed as tonnes/tonnes, but sometimes as bench cubic metres (bcm)/tonnes or bcm/bcm.
Tonne - Equal to 1,000 kilograms.
Qualified persons involved in the study
GRD Minproc managed the preparation of the Study which will be filed as a Technical Report on SEDAR and Greystar's web site within 45 days of this release.
All principal technical personnel and Qualified Persons ("QP") for the purpose of National Instrument 43-101, and Guidance Note for Mining, Oil and Gas Companies issued by the London Stock Exchange in respect of AIM companies, which outline standards of disclosure for mineral projects, participating in the Study and the future Technical Report have extensive relevant experience:
Marco Alfaro, QP employed by Metalica, was responsible for the validation of the resources model and mineral resources. Enrique Munoz QP also employed by Metalica was responsible for the reserves, Pit design and mine plan. Jack McPartland, QP president of McClelland Laboratories, was responsible for supervising the metallurgical test work and associated reporting. David Miranda, Mining Engineer, member of IIMCh (Chile) and AUSIMM (Australia), QP, Study and Process Manager of GRD Minproc Chile estimated the gold and silver recoveries and operating costs. Gonzalo Vargas, Electrical Engineer, Engineering Manager of GRD Minproc Chile, was responsible for the capital cost estimates. Jorge Fuentes, Chemical Engineer, Project Director from GRD Minproc Chile was responsible for the financial analysis reported herein. Dan Greig, QP and Principal Geologist and Resource Analyst from GRD Minproc, Perth, Australia was responsible for the overall compilation of the Study.
Frederick Felder QP, Executive Vice-President of Greystar, a geologist with more than 30 years of industry experience and a member in good standing with the Association of Professional Engineers and Geoscientists of British Columbia, is the Qualified Person for Greystar and has reviewed and approved the contents of this News Release.
All mineral resources have been estimated in accordance with the definition standards on mineral resources and mineral reserves of the Canadian Institute of Mining, Metallurgy and Petroleum referred to in National Instrument 43-101, commonly referred to as NI 43-101. U.S. reporting requirements for disclosure of mineral properties are governed by the United States Securities and Exchange Commission (SEC) Industry Guide 7. Canadian and Guide 7 standards are substantially different. This News Release uses the terms "measured", "indicated" and "inferred" resources. Mineral resources which are not mineral reserves do not have demonstrated economic viability. We advise investors that while those terms are recognized and required by Canadian regulations, the SEC does not recognize them. Inferred mineral resources are considered too speculative geologically to have economic considerations applied to them that enable them to be categorized as mineral reserves.
CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING INFORMATION: This news release includes certain "forward-looking statements" under applicable Canadian securities legislation. Such forward-looking statements or information, including but not limited to those with respect to the price of gold, estimated mineral resources and anticipated grades, expectations regarding gold/silver recovery rates, estimated internal rates of return, estimated future production, estimated costs of future production and anticipated time line to production. Forward looking statements are necessarily based upon a number of estimates and assumptions that, while considered reasonable to the Company, are subject to known and unknown risks, uncertainties, and other factors which may cause the actual results, performance or achievements of the Company to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements or information. Such factors include, among others, the actual price of gold, the factual results of current exploration, development and mining activities, changes in project parameters as plans continue to be evaluated, foreign exchange rate variations, conclusions or realization of mineral resources, risks relating to additional funding requirements, political and foreign risks, production risks, environmental regulation and liability, government regulation as well as other risk factors set out under the heading "Risk Factors" in the Annual Information Form of the Company dated March 25, 2008 which is available on SEDAR, as well as those factors disclosed in the Company's documents filed from time to time with the securities regulators in the Provinces of British Columbia and Ontario. Investors are cautioned not to put undue reliance on forward-looking statements due to the inherent uncertainty therein. The Company disclaims any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise.
SOURCE: Greystar Resources Ltd.
Greystar Resources Ltd. - Contact in Canada
David B. Rovig
President
(406) 245-9520
Greystar Resources Ltd. - Contact in Canada
Mr. Andreas Curkovic
Investor Relations
(416) 577-9927
Website: www.greystarresources.com
NCB Stockbrokers Limited - Contact in London
Christopher Caldwell
+44 (0) 20 7071 5200
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
