Riverstone Resources Inc.

Riverstone Resources Inc.

August 20, 2012 09:15 ET

Riverstone Announces Preliminary Economic Assessment Results on Flagship Karma Gold Project; After-Tax NPV of $192 Million and IRR of 37%

VANCOUVER, BRITISH COLUMBIA--(Marketwire - Aug. 20, 2012) - Riverstone Resources Inc. (TSX VENTURE:RVS)(OTCQX:RVREF)(FRANKFURT:3RV) ("Riverstone" or the "Company") is pleased to report the results of a NI 43-101 compliant Preliminary Economic Assessment (the "PEA") carried out on the Company's flagship Karma Gold Project in Burkina Faso, West Africa (the "Karma Project"). All currency figures are in $US and based on a $1,350/oz gold price (May 2012 three year trailing average).


  • Pre-tax NPV $271 M, IRR 47%.

  • After-tax NPV $192 M; IRR 37%; payback is 2 years; including the Burkina Faso Government 10% carried interest.

  • Open pit heap leach operation processing 3 Mtpa (million tonnes per annum) of oxide and transition mineralization to produce 70,000 to 90,000 oz of gold annually over a 10 year mine life and cash costs of $525/oz gold.

  • Initial start-up capital is $125 M, with a potential to reduce to $96 M utilizing contract mining.

  • The PEA is based on the January 1, 2012 NI 43-101 Global Mineral Inventory and optimized In-Pit resources.

  • In excess of 85,000 metres of drilling has been completed subsequent to the data cut-off date for the January 2012 resource estimation, which, have not been included in this PEA.

"We are very pleased with the robust results of this PEA which illustrate the potential economic viability of a mining operation for our flagship project. The strong economics demonstrated by the PEA support the company's strategic plan to develop a stand-alone heap leach operation and subsequently exploit the sulphide resource potential using the cash flow from the heap leach operations", commented Dwayne L. Melrose, President and CEO of Riverstone. "This is a significant milestone for the Company that will further guide the future development of the Karma Project to the feasibility stage. The additional 85,000 metres of drilling that have been completed since the last resource estimation have produced favourable results and is expected to further enhance the economics of the Karma Project. An important aspect of the Karma Project is the encouraging potential for further resource expansion as the mineralization is still open in at least one or more directions. Additionally, there is still excellent upside exploration potential throughout all the other properties owned and directed by the Company within Burkina Faso to discover new deposits."

The PEA examined the integrated development of the five deposits under three operating scenarios being compared to determine the most attractive option for development. These were:

  • Case 1: Heap Leach processing of all non-refractory resources
  • Case 2: CIL processing of all non-refractory resources
  • Case 3: Heap Leach processing of all non-refractory resources and flotation processing of a small portion of high-grade refractory resource
Summary Table
SCENARIO Case1 Case2 Case 3
Feed type NR NR NR R NR + R
Mine Life years 10 9 10 5 10
Ore Mined Mt 29.3 28.6 30.8 2.2 33.0
Average Grade g/t 0.88 0.89 0.87 2.34 0.97
Contained Gold Koz 828 819 860 165 1,025
Strip Ratio (waste:ore) w:o 2.5 2.6 2.8 7.8 3.2
Process Mtpa 3.0 3.0 3.0 0.4 3.2
Rate tpd 9,000 9,000 9,000 1,200 9,600
Average Recovery % 88 95 88 85 87
Recovered Gold Koz 728 776 754 140 889
PRE-TAX (incl NSR's, royalties)
NPV $ M 271 188 --- --- 227
IRR % 47 27 --- --- 34
NPV $ M 192 131 --- --- 157
IRR % 37 21 --- --- 26
Start-up Capital $ M 125 204 130 41 130
Payback years 2.0 3.2 --- --- 2.7
Cash Operating Cost $/oz 525 613 --- --- 648
Gold Gov't NSR Corporate Gov't F/C Discount
Price Royalty Rambo GGII Tax Interest Rate
$/oz % % % % % %
1,350 5.0 3.0 1.0 17.5 10.0 5.0
HL - Heap Leach; CIL - carbon in leach; FLOT - flotation; NR - non-refractory; R-refractory
Capital - start-up capital including working capital; Case 3 - HL and FLOT processing concurrently in years 5 - 10.

Riverstone will be hosting a conference call subsequent to the release of the PEA results. The call will be hosted by Dwayne Melrose, President and CEO and Peter Carter, Vice President, Engineering of Riverstone. Mr. Melrose and Mr. Carter will be available to respond to questions following a brief presentation. An Operator will direct participants to the call.

Conference Call Details:
Date: August 21, 2012
Conference Time: 10:00 am (Pacific)/ 1:00 pm (Eastern)
Conference ID: 4560664
Participant Dial-in Numbers: -North America - 416-644-3414/800-814-4859
-Germany -49-6958-999-0706/0800-101-1958
-United Kingdom - 44-20-7190-1595/0800-358-5271
Replay of the Call:
Access Code: 4560664#
Dial-in Numbers: 416-640-1917/877-289-8525
End Date: August 28, 2012

The PEA was managed by JDS Energy and Mining Inc. ("JDS"), Kelowna, BC (process/infrastructure/economics) and included work by other specialized firms as: P&E Mining Consultants Inc. ("P&E"), Brampton, ON (resources/mining), EBA A Tetra Tech Company, ("EBA") Vancouver, BC (geotechnical), and Roche Ltee, ("Roche") Montreal, Quebec (environmental) to produce a very solid PEA. JDS managed the PEA and produced the PEA document.


Resources for the PEA are based on assays from 105,000 m of RC and DDH drilling completed before September 2011 which are included in the NI 43-101 compliant resource estimate completed by P&E (see news release dated January 9. 2012 and NI 43-101 Technical Report titled "Technical Report and Resource Estimate on the Karma Project, Burkina Faso, West Africa" filed on SEDAR (www.sedar.com) February 23, 2012.) The resources are as follows:

Global Mineral Inventory - January 2012
TYPE g/t Mt g/t Koz Mt g/t Koz
Oxide 0.30 19.2 0.93 574 6.5 0.70 147
Transition 0.36 6.7 1.09 235 1.6 0.70 37
Sulphide 0.40 28.2 1.06 964 29.2 0.83 775
TOTAL 54.1 1.02 1,773 37.3 0.80 959
Optimized In-Pit Resources - January 2012
TYPE g/t Mt g/t Koz Mt g/t Koz
Oxide 0.30 17.9 0.96 555 5.0 0.76 123
Transition 0.36 6.0 1.15 222 1.0 0.79 24
Sulphide 0.40 23.4 1.14 857 12.9 1.01 419
TOTAL 47.3 1.07 1,634 18.9 0.93 566

All deposits are open down dip and in at least one direction along strike.

In September 2012, the resource model will be updated with the +85,000 m of additional drilling that has been completed after the cut-off date for the January 2012 resource estimation. The upcoming September 2012 resource update is designed to:

  • Convert Inferred to Indicated and Measured resource categories.
  • Potentially increase the Global Mineral Inventory to over 3 M oz gold.
  • Be utilized as the resource base for an anticipated project Definitive Feasibility Study ("DFS").


Pit optimization and the subsequent mine design exercise identified a potentially economic portion of the resources disclosed in January 2012 and are shown in the table below. A total of 83% of the process feed is in the Indicated category with the remaining 17% of the process feed is in the Inferred category. This highlights the high quality of the resource base that was used, de-risks the PEA results and limits the amount of additional drilling required for proceeding to a DFS.

The PEA contemplates that mining will be conducted using a fleet of seven - ten 91tonne trucks and two 15 m3 excavators in backhoe configuration working 5 m high benches. Mining rates, depending on the scenario, range from 30,000 to 40,000 tonnes per day with strip ratios of 2.5 to 3.2:1. Most of the oxide and transition material is free-digging with drilling and blasting required for the transition and sulphide rocks.

Potentially Economic Minable Resources by Scenario
Scenario Case1 Case2 Case 3
type NR NR NR R NR+R
Process Mt 29.3 28.6 30.8 2.2 33.0
Feed g/t 0.88 0.89 0.87 2.34 0.97
Koz 828 819 860 165 1025
Waste Mt 72.5 73.2 87.3 17.0 104.3
Total Mt 101.8 101.8 118.1 19.2 137.3
Strip Ratio w:o 2.5 2.6 2.8 7.8 3.2
(1) NR = Non-refractory R = Refractory


Metallurgical testing was carried out by Kappes, Cassidy & Associates of Reno, NV, U.S.A. Testing determined oxide recoveries are 90-95%; transition recoveries are 10% lower. Sulphide mineralization from Rambo and Nami are free-leaching with recoveries of 80-85%. Sulphide mineralization from Goulagou I, Goulagou II, and Kao is refractory with recoveries of 20-60%. Refractory mineralization had high (>90%) bulk flotation recovery and moderate (20-40%), but variable, gravity recovery.

Process Recoveries by Material Type and Scenario
Scenario Case1 Case2 Case 3
Oxide 90% 95% 90% ---
Transition 83% 95% 83% ---
Sulphide 81% 92% 81% 85% (2)
(1) NR = non-refractory; R =refractory
(2) 2-stage flotation

Test work, beyond the scope of the PEA, is underway to determine the optimum method for processing refractory material. This program includes comprehensive mineralogy and test work focused on but not limited to, methods amenable to low-cost, low grade processing such as BIOX and ALBION.


Heap Leach and CIL were determined to be suitable for processing of non-refractory material. A processing rate of 9,000 tpd (3.0 Mtpa) was identified as the best compromise between plant cost and throughput to generate annual production in each scenario of 70,000 to 90,000 oz of gold over a nominal 10 year mine life.

In Case 3, flotation of refractory mineralization to generate a direct-shipping concentrate was applied to a small (2.2 Mt), higher-grade (2.34 g/t gold) portion of the sulphide resource. Refractory feed processing was planned for a throughput of 1,200 tpd as an adjunct to heap leach, supplementing gold production in the latter years of the mine life when mined oxide grades decline.


The Exploitation permit for Goulagou I, Goulagou II, and Rambo was applied for in January 2012 and is expected to be received in Q4 2012 and for Kao in Q4 2013. The Nami exploration permit will not be converted to an Exploitation permit until additional exploration work to define this deposit is complete. All elements of the environmental permit for Goulagou I, Goulagou II, and Rambo are scheduled to be satisfied by mid-2013, allowing for the start of construction and mining thereafter. The Company owns a 90% interest in the Goulagou I and Goulagou II deposits and a 100% interest in the Kao, Rambo and Nami deposits, subject to a 10% free carried interest to the Burkina Faso government once transitioned from exploration to mining.


A Definitive Feasibility Study for Case 1 is expected to commence in Q4 2012 and to be completed in mid-2013. Construction could start in Q4 2013 with potential production commencing in Q4 2014. Filling the barrage (water reservoir) during the rainy season largely dictates when production could start. Opportunities to accelerate the project development schedule do exist and are largely dependent on the nature of the financing available.


Project capital costs by scenario are shown in the table below. Contract mining could reduce initial and total capital costs to $96 M and $123 M respectively, albeit with a decrease in project NPV. Equipment leasing and used equipment both offer opportunities to reduce capital costs further. In the table below, working capital is included in start-up capital and credited back to the project in sustaining capital.

Owner Operated Capital Costs by Scenario
Scenario Case 1 Case 2 Case 3
Capital Cost Units
Start-Up $ M 125 204 130 0 130
Sulphide Expansion $ M 0 0 0 41 41
Sustaining $ M 23 9 29 0 29
Closure $ M 3 3 3 0 3
Total $ M 151 216 161 41 202


All operating costs include contingency and reflect an appropriate mix of expatriate and national labour costs. Case 1 total cash operating costs are projected at $525/oz gold. Total unit cash operating costs for Case 2 and Case 3 respectively are $613/oz gold and $648/oz gold respectively.

Unit Operating Costs
Material type NR NR R
Mining $/t mined 1.62 1.60 1.70
Process $/t proc 6.21 9.78 55.24
Admin $/t proc 1.72 1.72 1.72
(1) NR = non-refractory; R = refractory
(2) Refractory process cost includes shipping and smelting


Project economics were modeled using the May 2012, three-year trailing average gold price of $US1,350/oz. Government royalties (5%) and NSRs for Rambo (3%) and Goulagou II (1%) were applied in all instances. Pre-tax financial performance was calculated for comparative purposes as shown in the Table below.

Pre-Tax Financial Performance by Scenario
Scenario Case1 Case2 Case3
Feed type NR NR NR+R
NPV @ 5% $ M 271 188 227
IRR % 47 27 34
(1) NR = non-refractory; R = refractory

After-tax financial performance was determined to illustrate absolute project value. This evaluation includes a 17.5% corporate tax and a payment of the10% free-carried government interest.

After-Tax Financial Performance by Scenario
Scenario Case1 Case2 Case3
Feed type NR NR NR+R
NPV @ 5% $ M 192 130 157
IRR % 37 21 26
Payback yrs 2.0 3.2 2.7
(1) NR = non-refractory; R = refractory

In both pre-tax and after-tax scenarios, Case 1 generates the optimal financial performance by virtue of its low capital and operating costs. Case 2 delivered the least optimal financial performance as the high recovery from CIL could not offset higher capital and operating costs. Case 3 delivered the second most beneficial financial performance by supplementing heap leach production with gold generated from processing refractory resources.

At presently projected costs, the refractory processing scenario in Case 3 does not pay back the investment in the flotation plant at the base case gold price. At gold prices >$1,920/oz, Case 3 delivers higher NPV than Case 1 on the strength of its greater leverage to the price of gold in the form of higher total gold production. The risk to adopt Case 3 is minimal as the:

  • Heap leach investment is paid off prior to a refractory processing decision.
  • Flotation plant design and construction can be completed rapidly (12 months).
  • Pre-stripping of sulphide resources can be suspended if the future gold price is unattractive

On an after-tax basis, Case 1 has very robust economics in terms of rapid (2 year) payback, low cash operating costs of $525/oz, and a low breakeven gold price of $830/oz, which is about half the current spot price. If capital or operating costs rise 20%, NPV remains greater than $150 M; if grade or gold price decline 18%, NPV is greater than $100 M; and if the discount rate is increased to 15%, NPV is still greater than $80 M.

The PEA is considered preliminary in nature and includes Inferred Mineral Resources that are considered too speculative geologically to have the economic considerations applied to them that would enable them to be categorized as Mineral Reserves. Mineral Resources that are not Mineral Reserves have not yet demonstrated economic viability. Due to the uncertainty that may be attached to Inferred Mineral Resources, it cannot be assumed that all or any part of an Inferred Mineral Resource will be upgraded to an Indicated or Measured Mineral Resource as a result of continues exploration or Mineral Reserves once economic considerations are applied. Therefore there is no certainty that the production profile concluded in the PEA will be realized.


The Karma Project demonstrates significant upside future potential:

  • An updated resource estimate which will include an additional 85,000 m of drilling that has been completed since the data cut-off date for the previous resource estimate based on 105,000 m of drilling on which the PEA is based. The new updated resource estimate is expected to be completed in September, 2012 and has the potential to increase the Global Mineral Inventory to over 3 million oz of gold.

  • Good exploration potential to expand the current resources of the five deposits on which the PEA is based, as the five deposits are all open in at least one direction and some are open in all directions.

  • Good exploration potential to locate new resources peripheral to existing deposits on exploration targets that have been defined to enhance any potential mining operation.

  • Good exploration potential to locate new resources throughout the Company's other landholdings that could benefit any potential stand alone mining operation.

  • Case #1 predominantly exploits oxide and transition zone mineralization. There is potential to have concurrent production from both heap leach and other milling operations to maximize the potential of the entire resource.

An NI 43-101 compliant technical report supporting this PEA will be completed by JDS Energy & Mining Inc., and filed on SEDAR within 45 days of the date of this press release. Wayne Corso, P. E., Vice President of Engineering of JDS and Eugene Puritch, P.Eng., President of P&E Mining Consultants Inc. have reviewed and approved the contents of this news release. Dr. Giles Peatfield, Ph.D., P.Eng.is Riverstone's Qualified Person for the purposes of NI 43-101 and has reviewed and approved the technical content of this news release.

Riverstone is active in Burkina Faso, West Africa, where it holds a portfolio of four high quality exploration projects covering in excess of 2,000 square kilometres. Addition information about the Company and its activities may be found on the Company's website at www.riverstoneresources.com and under the Company's profile at www.sedar.com.


Dwayne L. Melrose, President & CEO

Giles R. Peatfield, Ph. D., P.Eng. is the Qualified Person for RVS and has reviewed and approved the contents of this release.

Certain statements made and information contained in this news release and elsewhere constitutes "forward-looking information" within the meaning of Canadian securities legislation. Forward-looking statements are based on certain assumptions and are subject to risks and uncertainties which could cause actual events or results to differ from those reflected in the forward-looking statements, including, without limitation, with respect to statements regarding the updated resources estimate, anticipated timing and completion of a definitive feasibility study, mine development schedule, the granting of exploitation permits, the anticipated timing an completion of a NI 43-101 compliant technical report supporting the PEA, the assumptions set forth in this news release and in the Company's news release of January 9, 2012, and risks and uncertainties relating to the interpretation of drill results and the estimation of mineral resources, the geology, grade and continuity of mineral deposits, the possibility that future exploration, development results will not be consistent with the Company's expectations, accidents, equipment breakdowns, risk of undiscovered, title defects and surface access, labour disputes, the potential for delays in exploration and permitting activities, the potential for unexpected costs and expenses, commodity price fluctuations, currency fluctuations, political risk and other risks and uncertainties, including those described under Risk Factors in each management discussion and analysis and in the Company's annual information form which are available under the Company's profile at www.sedar.com. Forward-looking information is based on various assumptions including, without limitation, the expectations and beliefs of management, the assumed long term price of gold, that the Company will receive required permits and access to surface rights, that the Company can access financing, appropriate equipment and sufficient labour and that the political environment within Burkina Faso will continue to support the development of environmentally safe mining projects. Should one or more of these risks and uncertainties materialize, or should underlying assumptions prove incorrect, actual results may vary materially from those described in forward-looking statements. Accordingly, readers are advised not to place undue reliance on forward-looking statements.

This news release may use the terms "measured", "indicated" and "inferred" as these terms are defined under Canada's National Instrument 43.101. U.S. Investors are advised that, while such terms are recognized and required by Canadian regulations, they are not recognized by the United States Securities and Exchange Commission ("SEC") and may not be comparable to similar information for United States mining or exploration companies. As such, certain information contained on this news release concerning descriptions of mineralization and resources under Canadian standards is not comparable to similar information made public by United States companies subject to the reporting and disclosure requirements of the SEC. U.S. investors are cautioned not to assume that any part or all of the mineral deposits described in these categories will ever be converted into proven or probable reserves, as defined in the SEC's Industry Guide No. 7.

Neither TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.

Contact Information

  • Riverstone Resources Inc. - Vancouver Office
    Dwayne L. Melrose

    Riverstone Resources Inc.
    Don Mosher
    Corporate Development

    Riverstone Resources Inc.
    Raju Wani
    Investor Relations

    Riverstone Resources Inc.
    Ron Cooper
    Investor Relations