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April 19, 2016
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.
Highlights
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
Kamituga
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)
Twangiza
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
Namoya
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
TOTAL MINERAL RESERVE
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.
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