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Key Assumptions
Below are the key assumptions, parameters and methods used to estimate the Lugushwa and Namoya Mineral Resources:
-- wireframing was restricted to borehole intersections above a 0.3 to 0.5g/t Au cut-off grade for Lugushwa and 0.4g/t Au for Namoya, 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 20m N-S (along strike), 20m E-W (across strike) and 10m in the vertical direction;-- estimation used dynamic anistotropy;-- Datamine Studio 3TM was the modelling package; and-- at all times, the relationship between geology and preliminary 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 pulverised down to 90% passing 75 microns. Approximately 150 grams of the pulverised sample was then shipped to the SGS Laboratory (which is independent of the Company) in Mwanza, Tanzania where the samples were analysed for gold by fire assay using a 50g charge. As part of the Company's QA/QC procedures, internationally recognised standards, duplicates and blanks were inserted into the sample batches.
Drill core samples were respectively taken from Lugushwa, Namoya, Twangiza East and West to determine relative density measurements for the various deposits and the oxide, transitional and fresh rock components.
The key assumptions used for the determination of the In-pit M&I Mineral Resources at Namoya are tabled below:
----------------------------------------------------------------------------Input Data Units----------------------------------------------------------------------------Gold price US$1,500 per ounce----------------------------------------------------------------------------Mining dilution 5% at zero grade----------------------------------------------------------------------------Pay limit for high grade 1.0 g/t Au----------------------------------------------------------------------------Stockpile ore 0.4 g/t-1.0 g/t Au----------------------------------------------------------------------------Waste less than 0.4 g/t Au----------------------------------------------------------------------------Mining recovery 95%----------------------------------------------------------------------------Pit slopes Minus 40 to 50 degrees----------------------------------------------------------------------------Metallurgical recovery Oxides (88%), Transitional (84%), Fresh (80%)----------------------------------------------------------------------------
The Twangiza resource model was built by SRK and most recently published in a Banro press release dated March 4, 2011. Apart from the Twangiza East and West estimates, the current estimates employed the SRK model but with changes to the economic assumptions with the improved cost.
For more details, refer to the technical report of Senet dated March 9, 2011 (as revised on March 24, 2011) and entitled "Economic Assessment NI 43-101 Technical Report, Twangiza Phase 1 Gold Project, South Kivu Province, 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.
