Home / Mining Company News Releases (Unreviewed) / Banro Announces Reserve Growth of 9% to 3.18 Million Ounces After Depletion in Twangiza and Namoya

Banro Announces Reserve Growth of 9% to 3.18 Million Ounces After Depletion in Twangiza and Namoya

TORONTO, CANADA–(Marketwired – April 19, 2016) – Banro Corporation (“Banro” or the “Company”) (NYSE MKT:BAA)(TSX:BAA) is pleased to provide an update of its Mineral Resource and Mineral Reserve estimates at its wholly-owned projects on the Twangiza-Namoya gold belt in the Democratic Republic of the Congo (the “DRC”). The annual review of Mineral Resources and Mineral Reserves at the Company’s four core projects, Twangiza, Namoya, Lugushwa and Kamituga, has resulted in a replacement of depleted ore and an increase in Mineral Reserves at both Twangiza and Namoya.


  • The Twangiza Proven and Probable Mineral Reserves increased by 11% to 1.82 million ounces (“Moz”) of gold (27.67Mt @ 2.05g/t Au) after depletion due to changes in cut-off grade, reversal on bulk density and revision of the pit design. This gives Twangiza a 14-year mine life.
  • At Namoya, the Proven and Probable Mineral Reserves have increased by 7% to 1.36 Moz of gold (20.94Mt @ 2.02g/t Au) after depletion, revision of the pit designs, addition of gold-in-process and additional drilling results at the Namoya Summit – Filon B portion of the Namoya Summit deposit.
  • Banro’s overall Mineral Reserves have grown by 9% to 3.18 Moz of gold (48.61Mt @ 2.03g/t Au) at US$1,200/oz gold price.
  • Banro’s total Measured and Indicated Mineral Resources for all its properties is 7.04 Moz of gold (141.94Mt @ 1.54g/t Au), and Inferred Mineral Resources of 5.08 Moz of gold (93.29Mt @ 1.70g/t Au).

“The reserve growth at both Twangiza and Namoya is consistent with Banro’s drive to continuously replace depleted reserves owing to near mine convertible resources and progressively improving on efficiencies through waste reduction and cost containment initiatives,” commented Banro CEO and President, John Clarke.

During 2014, the Company scaled down its exploration activities at its Twangiza, Namoya, Lugushwa and Kamituga projects and focused its geological expertise in supporting production growth at Twangiza and mine development at the Namoya Mine, and further identification of near mine high grade targets.

In order to consolidate Banro’s position on the various exploration sites, some limited exploration activities were carried out in 2015 using small teams focused on generating new oxide targets in Lugushwa and Kamituga. At Namoya, exploration drilling activities focused on near mine resource upgrade and target generation activities. The primary objective was to upgrade Inferred Resources within the Namoya Summit-Filon B reserve pit into a higher confidence resource for conversion into mineral reserves. In addition, near mine oxide resources were defined within 5 kilometers of the Run-Of-Mine pad. At Twangiza, the focus was on the optimization of mine to mill reconciliation processes.

Banro’s Mineral Resources and Mineral Reserves disclosed in this press release are reported in accordance with National Instrument 43‐101 (Standards of Disclosure for Mineral Projects), which incorporates by reference the CIM Definition Standards on Mineral Resources and Mineral Reserves. The Mineral Resources reported in this press release are inclusive of the Mineral Reserves component.

Mineral Resource and Mineral Reserve Declaration at December 31, 2015

Table 1: Mineral Resources

Mine/Project/Category As at December 31, 2014 As at December 31, 2015
Tonnes Grade Gold Tonnes Grade Gold
(Mt) (g/t Au) (Moz) (Mt) (g/t Au) (Moz)
Twangiza (Oxide)
Measured 3.72 2.30 0.28 2.49 1.99 0.16
Indicated 8.76 1.88 0.53 8.57 1.86 0.51
Measured & Indicated 12.48 2.02 0.81 11.06 1.89 0.67
Inferred 1.34 1.32 0.06 1.56 1.20 0.06
Twangiza (Transition & Fresh)
Measured 3.80 2.23 0.27 3.11 2.11 0.21
Indicated 93.00 1.40 4.18 85.18 1.40 3.81
Measured & Indicated 96.80 1.43 4.45 88.29 1.42 4.02
Inferred 11.65 1.12 0.42 8.27 1.17 0.31
Namoya (Oxide & Free-milling)
Measured 22.95 1.95 1.44 20.44 2.02 1.33
Indicated 5.78 1.61 0.30 5.24 1.73 0.29
Measured & Indicated 28.72 1.88 1.74 25.68 1.96 1.62
Inferred 6.35 1.63 0.33 5.03 1.63 0.26
Lugushwa (Oxide)
Indicated 16.91 1.35 0.73 16.91 1.35 0.73
Inferred 6.17 1.56 0.31 6.17 1.56 0.31
Lugushwa (Transition & Fresh)
Inferred 65.01 1.54 3.22 65.01 1.54 3.22
Inferred (Surface) 4.14 2.40 0.32 4.14 2.40 0.32
Inferred (Underground) 3.12 6.00 0.60 3.12 6.00 0.60
TOTAL MEASURED & INDICATED 154.91 1.55 7.73 141.94 1.54 7.04
TOTAL INFERRED 97.78 1.67 5.26 93.29 1.70 5.08

Mineral Resource

Banro’s Measured and Indicated (“M&I”) Mineral Resource has decreased by 8.93% to 7.04 Moz (141.94Mt @ 1.54g/t Au) (December 31, 2014: 7.73 Moz representing 154.91Mt @ 1.55g/t Au), and Inferred Mineral Resources have decreased by 3.42% to 5.08 Moz (93.29Mt @ 1.70g/t Au) (December 31, 2014: 5.26 Moz representing 97.78Mt @ 1.67g/t Au). The reduction in the Mineral Resource is mainly attributed to the revision of the optimized pit and mining depletion. The Mineral Resource estimates discussed in this press release for Namoya, Lugushwa and Twangiza consist of in situ Mineral Resources at a 0.4 g/t Au cut-off constrained within a US$1,600 per ounce optimized pit shell.

The underground Mineral Resources at Kamituga are those situated below the Mobale open pit, estimated using historical underground information at a cut-off grade of 1.5 g/t Au. The Mineral Resource estimates for Kamituga were prepared by SRK Consulting (UK) Ltd (then Steffen, Robertson and Kirsten (UK) Ltd) (“SRK”), using historical data and were included in the February 2005 NI 43-101 technical report prepared by SRK for Banro (this report is entitled, “NI 43-101 Technical Report Resource Estimation and Exploration Potential at the Kamituga, Lugushwa and Namoya Concessions, Democratic Republic of Congo”). These estimates have not been updated. Banro has since 2011 carried out extensive exploration including some amount of drilling to verify the historical results at Kamituga. Further work planned, especially drilling work to update the Kamituga resource, was deferred as the focus shifted to mine development at Namoya and the process plant optimization at the Twangiza mine.

Below are the key assumptions, parameters and methods used to estimate the Twangiza, Lugushwa and Namoya Mineral Resources:

  • Wireframing was restricted to borehole intersections above a 0.3 to 0.5 g/t Au cut-off grade for Lugushwa and 0.4g/t Au for Namoya and Twangiza East and West;
  • Gold grades have been determined using Ordinary Kriging interpolation into a 3-dimensional block model constrained by mineralization wireframes;
  • The mineralization models were constrained within the wireframe with primary block dimensions of 20 metres N-S (along strike), 20 metres E-W (across strike) and 10 metres in the vertical direction;
  • Estimation used dynamic anisotropy;
  • Datamine Studio 3TM was the modelling package; and
  • At all times, the relationship between geology, mining and economic factors was taken into account.

Drill cores for assaying were taken at a maximum of one metre intervals and were cut with a diamond saw with one-half of the core placed in sealed bags and sent to the Company’s sample preparation facility in Bukavu, DRC. The core samples were then crushed down to minus 2 mm, and split with half of the sample pulverized down to 90% passing 75 microns. Approximately 150 grams of the pulverized sample was then shipped to the SGS Laboratory (which is independent of the Company) in Mwanza, Tanzania where the samples were analyzed for gold by fire assay using a 50g charge. As part of the Company’s QA/QC procedures, internationally recognized standards, duplicates and blanks were inserted into the sample batches.

Drill core samples were respectively taken from Lugushwa, Namoya, and Twangiza East and West to determine relative density measurements for the various deposits and the oxide, transitional and fresh rock components.

Mineral Reserve

Table 2: Mineral Reserves

As at December 31, 2014 As at December 31, 2015
Mine/Project/Category Tonnes Grade Gold Tonnes Grade Gold
(Mt) (g/t Au) (Moz) (Mt) (g/t Au) (Moz)
Proven 7.47 2.41 0.58 6.21 2.19 0.44
Probable 14.91 2.22 1.06 21.47 2.01 1.39
Proven and Probable 22.38 2.28 1.64 27.67 2.05 1.82
Proven 18.44 1.98 1.17 17.90 2.10 1.21
Probable 2.09 1.43 0.10 3.04 1.53 0.15
Proven and Probable 20.53 1.92 1.27 20.94 2.02 1.36
Proven 25.91 2.10 1.75 24.10 2.12 1.65
Probable 17.00 2.12 1.16 24.50 1.95 1.54
Total Proven and Probable 42.91 2.11 2.91 48.61 2.03 3.18
Note: Rounding of numbers may result in computational discrepancies.
Mineral Reserves are included in Mineral Resources.

The Twangiza Proven and Probable Mineral Reserve has increased by 11% to 1.82 Moz (27.67Mt @ 2.05g/t Au) from 1.64 Moz (22.38Mt @ 2.28g/t Au) (December 31, 2014). This 11% increase in reserves after depletion is a function of changes in cut-off grade, reversal on bulk density, and revision of the pit design.

The reconciliation exercise previously carried out under the supervision of SRK from March to June 2015 recommended a revision of the bulk densities of the top 15m of material in the Twangiza Main and North pits, from an average of 2.05 t/m3 to 1.80 t/m3 and 1.89 t/m3, respectively. Due to the extensive degree of weathering and artisanal mining, a further 19.5% discount was applied to the overall bulk densities of the measured component of the Twangiza Main pit. The results of this exercise were reflected in the Twangiza Proven and Probable Mineral Reserve as at December 31, 2014.

The results of the systematic monitoring mechanism put in place to track the modification on a monthly basis in the Twangiza Main pit, has demonstrated the need to apply a 13% increase to the overall model fill volume and a 4.9% increase to the overall bulk density. A further 4% was applied to the ore fill volume within the areas which were affected by the recommendations. Additionally, the grade control rip-lines provided extra information which was to refine the ore and waste boundaries and hence their distribution in portions of the measured category of the Resource model.

The Twangiza Main pit design was modified for the ultimate reserves pit to have a ramp on the southern side as recommended by SRK in the NI 43-101 technical report which was published on July 29, 2015. The relocation of the ramp to the southern side of the ultimate reserve pit accounts for the relative growth in reserve of the non-oxide material.

Table 3: The key assumptions used for the determination of the Mineral Reserves at Twangiza

Input data Units
Gold price US$ 1,200 per ounce
Mining costs US$ 3.26/tonne mined
Processing costs US$ 18.13/tonne processed
General and administration costs US$ 10.30/tonne processed
Royalties and selling costs US$ 79.58/ounce
Mining dilution 5% at zero grade
Reserves cut-off grade 0.79 g/t Au recoverable
Mining recovery 100%
Pit slopes 30 to 50 degrees
Metallurgical recovery
Oxides Main 88.0 %
North 89.0 %
Transition FP Main 77.6 %
North 90.9 %
Fresh FP Main 73.0 %
North 79.4 %
Transition CMS Main 35.5 %
North 35.6 %
Fresh CMS Main 50.4 %
North 50.5 %

The Proven and Probable Mineral Reserve estimate at Namoya has increased by 7% to 1.36 Moz (20.94Mt @ 2.02g/t Au inclusive of 63,137oz GIP) from 1.27 Moz (20.53Mt @ 1.92g/t) (December 31, 2014). Revision in pit designs and the additional drilling of the Namoya Summit Filon-B deposit has brought in replacement of the 2015 depletion and an additional growth of 7% in reserves.

Table 4: The key assumptions used for the determination of the Mineral Reserves at Namoya

Input data Units
Gold price US$ 1,200 per ounce
Mining costs US$ 3.15/tonne mined
Processing costs US$ 10.30/tonne processed
General and administration costs US$ 5.78/tonne processed
Royalties and selling costs US$ 66.63/ounce
Mining dilution 5% at zero grade
Reserves cut-off grade 0.43 g/t Au recoverable
Mining recovery 100%
Pit slopes 40 to 50 degrees
Metallurgical recovery Oxides (88%), Transitional (84%), Fresh (80%)

The Twangiza resource model was originally built by SRK and the model, appropriately depleted, was used in the Banro press release dated March 4, 2011. The current estimates employed the SRK model but with changes to the economic assumptions to reflect current economic trends in the gold market, bulk density adjustments, and updated depletion.

For more details, refer to the technical report of SRK dated July 29, 2015 and entitled “NI 43-101 Technical Report, Mineral Resource and Reserve Update, December 31, 2014, Twangiza Gold Mine, Democratic Republic of the Congo”, which has been filed on, and can be obtained from, SEDAR at www.sedar.com and EDGAR at www.sec.gov.

Qualified Person

Banro’s Head of Projects and Operations, Daniel K. Bansah, MSc (MinEx), who is a Chartered Professional Member of The Australasian Institute of Mining and Metallurgy (MAusIMM(CP)) and a “qualified person” (as such term is defined in National Instrument 43-101), is responsible for the Twangiza, Lugushwa and Namoya Mineral Resource estimates and Twangiza and Namoya Mineral Reserve estimates disclosed in this press release as well as the other technical information contained in this press release. Mr. Bansah has reviewed and approved the contents of this press release.

Banro Corporation is a Canadian gold mining company focused on production from the Twangiza mine, which began commercial production September 1, 2012, and the ramp-up to full production at its second gold mine at Namoya, where commercial production was declared effective January 1, 2016. The Company’s longer term objectives include the development of two additional major, wholly-owned gold projects, Lugushwa and Kamituga. The four projects, each of which has a mining license, are located along the 210 kilometre-long Twangiza-Namoya gold belt in the South Kivu and Maniema provinces of the Democratic Republic of Congo (“DRC”). All business activities are followed in a socially and environmentally responsible manner.

Cautionary Note to U.S. Investors

The United States Securities and Exchange Commission (the “SEC”) permits U.S. mining companies, in their filings with the SEC, to disclose only those mineral deposits that a company can economically and legally extract or produce. Certain terms are used by the Company, such as “Measured”, “Indicated”, and “Inferred” “Resources”, that the SEC guidelines strictly prohibit U.S. registered companies from including in their filings with the SEC. U.S. Investors are urged to consider closely the disclosure in the Company’s Form 20-F Registration Statement, File No. 001-32399, which may be secured from the Company, or from the SEC’s website at http://www.sec.gov/edgar.shtml.

Cautionary Note Concerning Mineral Resource and Mineral Reserve Estimates

The Company’s Mineral Resource and Mineral Reserve figures are estimates and no assurances can be given that the indicated levels of gold will be produced. Such estimates are expressions of judgment based on knowledge, mining experience, analysis of drilling results and industry practices. Valid estimates made at a given time may significantly change when new information becomes available. While the Company believes that the Mineral Resource and Mineral Reserve estimates included in this press release are well established, by their nature Mineral Resource and Mineral Reserve estimates are imprecise and depend, to a certain extent, upon statistical inferences which may ultimately prove unreliable.

Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability. There is no certainty that Mineral Resources can be upgraded to Mineral Reserves through continued exploration.

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 continued exploration. Confidence in the estimate is insufficient to allow meaningful application of the technical and economic parameters to enable an evaluation of economic viability worthy of public disclosure (except in certain limited circumstances). Inferred Mineral Resources are excluded from estimates forming the basis of a feasibility study.

Cautionary Note Concerning Forward-Looking Statements

This press release contains forward-looking statements. All statements, other than statements of historical fact, that address activities, events or developments that the Company believes, expects or anticipates will or may occur in the future (including, without limitation, statements regarding estimates and/or assumptions in respect of Mineral Resource and Mineral Reserve estimates, future gold production, mine life extension, gold recoveries, costs, potential Mineral Resources and Mineral Reserves and the Company’s production, development and exploration plans and objectives) are forward-looking statements. These forward-looking statements reflect the current expectations or beliefs of the Company based on information currently available to the Company. Forward-looking statements are subject to a number of risks and uncertainties that may cause the actual results of the Company to differ materially from those discussed in the forward-looking statements, and even if such actual results are realized or substantially realized, there can be no assurance that they will have the expected consequences to, or effects on the Company.
Factors that could cause actual results or events to differ materially from current expectations include, among other things: uncertainty of estimates of capital and operating costs, production estimates and estimated economic return of the Company’s projects; the possibility that actual circumstances will differ from the estimates and assumptions used in the economic studies of the Company’s projects; failure to establish estimated Mineral Resources and Mineral Reserves (the Company’s Mineral Resource and Mineral Reserve figures are estimates and no assurance can be given that the intended levels of gold will be produced); fluctuations in gold prices and currency exchange rates; inflation; gold recoveries being less than expected; uncertainties relating to the availability and costs of financing needed in the future; changes in equity markets; political developments in the DRC; lack of infrastructure; failure to procure or maintain, or delays in procuring or maintaining, permits and approvals; lack of availability at a reasonable cost or at all, of plants, equipment or labour; inability to attract and retain key management and personnel; changes to regulations affecting the Company’s activities; the uncertainties involved in interpreting drilling results and other geological data; and the other risks disclosed under the heading “Risk Factors” and elsewhere in the Company’s annual information form dated March 28, 2016 filed on SEDAR at www.sedar.com and EDGAR at www.sec.gov. Any forward-looking statement speaks only as of the date on which it is made and, except as may be required by applicable securities laws, the Company disclaims any intent or obligation to update any forward-looking statement, whether as a result of new information, future events or results or otherwise. Although the Company believes that the assumptions inherent in the forward-looking statements are reasonable, forward-looking statements are not guarantees of future performance and accordingly undue reliance should not be put on such statements due to the inherent uncertainty therein.

Banro Corporation
Martin Jones
+1 (416) 366-2221, Ext. 3213
+1-800-714-7938, Ext. 3213
[email protected]


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