Tonguma Project

  • Location The Tonguma Project is located in the Lower Bambara Chiefdom, Kenema District, approximately 68 km south of the Koidu Kimberlite Project. The project area measures 142.1 km² and consists of the Tongo Diamond Field Project (88.5 km²) and the Panguma Project (53.6 km²), which have been combined to form the Tonguma Project.
  • Tenure The Tongo Diamond Field Exploration Licence (EXPL 4/04), secured by Koidu Holdings in May 2004, was converted to a Mining Lease in July 2008 after the successful completion of a bulk sampling programme and underground mining feasibility study. The timing coincided with the commencement of the Government of Sierra Leone's Mining Review Process. Development of the property was put on hold until this process had run its course and a Mining Lease Agreement entered into between Government and the Company.
  • Tenure The Panguma Exploration Licence became available in 2008 and Koidu Holdings application to explore this property was granted in October 2008. The property hosts the along-strike extensions of the kimberlite dyke zone within the Tongo Mining Lease. The Company demonstrated that incorporating the Panguma property into the Tongo Mining Lease would be beneficial and applied to Government to consider this option. The concept was approved and the Tongo Diamond Field Project and Panguma Exploration Licence areas were combined to form the Tonguma Project.
  • Geology The Tonguma Project hosts a number of kimberlite dyke zone and small enlargements (blows) along these dyke zones. In addition to the historically reported Lando, Kundo, Tongo and Peyima dyke zones , several new discoveries have been made by Koidu Holdings and the artisanal miners working in the area.
  • Historical Data Historical maps and reports provided diamond distribution patterns and sampling data for the Lando dyke zone and the Peyima blow. Kimberlite grades for the Lando ranged from 2.68 to 3.62 carats per tonne, while the Peyima Blow was reported to have a grade of 0.42 carats per tonne.
  • Koidu Holdings S.A appointed Cemmats Group Limited to undertake the Environmental Baseline Study in order to identify environmental and social issues that would need to be considered. Cemmats conducted a preliminary site visit, from 11 to 13 June 2004 to determine the scope of work for their proposal and to initiate the public consultation and disclosure process. On approval of Cemmats proposal in August 2004, work on the Environmental Baseline Study commenced.
  • Consultation & Disclosure Cemmats addressed the local community and chiefdom authorities in order to explain the purpose and objectives of the study. Questionnaires were administered to residents in the villages within the study area to obtain data on several issues including water supply and quality, sanitation, socio-economic and socio-cultural issues. Cemmats held a focused group discussion with various stakeholders in the alluvial diamond mining industry in the area to inform them of the proposed exploration activities and obtain their views especially with respect to the artisanal alluvial operations. The meeting was attended by 57 stakeholders comprising miners, Diamond Dealers, Chiefs, Licence Holders, Bush Owners, Representatives of Peace Diamond Alliance, Mines Monitoring Officers and Mine Wardens.
  • Consultation & Disclosure A public meeting held at the Tongo court barry introducing Koidu Holdings S.A. to the community.
  • Consultation & Disclosure Chief Executive Officer, Jan Joubert, explained Koidu Holdings' work programme to the Government representatives, Chiefdom authorities and the local community.
  • Environmental Baseline After the public meeting, Koidu Holdings undertook an aerial survey of the licence area by helicopter, taking photographs and noting important features that would impact on the detailed planning and implementation of the proposed work programme. During the survey it was evident that significant damage to the environment had been caused by extensive commercial and artisanal mining over the past 50 years, and that the close proximity of villages to the dyke zones which were to be sampled would require careful consideration and interaction with the local community.
  • Environmental Baseline The project area comprises six settlements, namely: Kpandebu, Palima, Mavehun Tokpombu, Sandeyeima and Tongola. All are located and influenced by mining activities within the project area. A total of 680 households (4,555 people) occupied 250 houses within the licence area at the time of the survey. Of these, 250 heads of households representing 2,041 people were interviewed by Cemmats during the social survey.
  • Environmental Baseline Artisanal mining is the main economic activity of a majority of the active male population in the area. During the survey, it was found that the main occupation of 38% of the household heads was mining, followed by 32% engaged in farming and 22% in business activities such as trading.
  • Water Public water supply infrastructure does not exist within the area. Water for domestic and other uses is obtained from shallow wells. Faecal-indicator bacteria were discovered in all the wells tested, in different proportions.
  • Environmental Baseline Other issues that emerged during Cemmats' baseline study were that there was limited accessibility due to poor condition of roads between Tongo and Kenema and Tongo and Koidu; the airstrip requires rehabilitation; there were no landline telephone or postal services; Cellphone communication was introduced in October 2005; there was no source of main power supply in Tongo. Small diesel driven generators supply power to the more affluent households; there are no hospital facilities. Only one community heath centre is in operation.
  • Exploration Programme The exploration strategy followed by Koidu Holdings was to verify the reported high historical grades of the Lando dyke zone and to extend the bulk sampling to the Kundu dyke zone as a first phase, and if the high historical grades were confirmed, to follow on with a drilling programme and further bulk sampling. The sites along the Lando and Kundu were selected based on proximity to historical sampling sites and accessibility. The objective of the bulk sampling was to simulate as closely as possible the results that could be achieved during underground mining, i.e. sampling of hard rock kimberlite rather than decomposed kimberlite, and processing the whole sampling/mining width slot, including waste, in order to obtain a representative mining grade for each dyke zone. The narrowness of the dyke lenses (between 10 cm and 37 cm) within the 1-1.5m mining width means that significant volumes of waste (up to 90%) had to be mined and processed.
  • Exploration Programme MSA Geoservices (Pty) Ltd, a South African based consulting company specialising in exploration in Africa, was contracted to independently supervise the bulk sampling programme and to ensure the representivity and integrity of the samples from the point of extraction to the conclusion of the sale. MSA were responsible for: Mapping the dyke exposure at the surface of the approximately 1m wide hard rock excavation, as well as at the base after sample extraction; Photographing the dyke exposures; Controlling the loading and hauling of the bulk samples to the stockpile at Tongo; Controlling the loading and hauling of bulk samples from the Tongo stockpile to the stockpile at Koidu; Ensuring the chain of custody of the diamonds recovered was intact from extraction to valuation and export.
  • Exploration Programme Drilling of the Lando A Dyke Zone
  • Lando Mapping and Bulk Sampling The excavation along the Lando dyke zone revealed two discrete dyke units, named Lando A and Lando B, each of which shows considerably more horse tailing and variability in dyke widths than the single main Kundu dyke. Strike orientations of the Lando A dyke lenses range from 054° to 062°, with an end to end strike average of 056°. Lando B strike measurements range from 065° to 072°, with an average orientation of 066°. The dips of the Lando A and B dyke zones varied from vertical to between 80-85°.
  • Kundu Mapping and Bulk Sampling The Kundu dyke zone displayed less variability in the morphology of the dyke lenses, as well as in the strike orientations and dip. The strike ranged from 061° to 063° and the dip remained vertical in the area sampled.
  • Loading and Hauling of Samples The mixed waste and ore from each blast was loaded by excavator onto 25 tonne ADTs and hauled to the interim stockpile area near the Tongo Field camp, where the sample was consolidated prior to transportation to Koidu. Each excavator load and truck load was counted and recorded by the grade control officers. The sample transport process from excavation at Tongo to offloading in the correct stockpile area at Koidu was strictly controlled by the grade control teams at Tongo and Koidu, and monitored by MSA.
  • Bulk Sampling Results Three textural types of kimberlite have been identified.
  • Exploration Programme After sample extraction at the Lando B excavation.
  • Petrography Samples of the Lando A, Lando B and Kundu dyke were sent to the Council for Scientific and Industrial Research (CSIR) in South Africa for petrographic analysis. The mineralogy of the all three magmatic, macrocrystic kimberlite samples is similar, containing olivine and phlogogpite xenocrysts and phenocrysts in a groundmass of phlogopite and spinel. According to the CSIR, the diamond-potential interest rating of the Kundu dyke is the highest of all three dykes as it contains very large quantities of olivine xenocrysts, small quantities of olivine phenocrysts (although somewhat large) and abundant fine-grained spinels, suggesting very good diamond carrying capacity potential coupled with moderate to high diamond preservation potential.
  • Diamond Recoveries The concentrates from the Flowsort X-Ray machines and the grease table at the 50 tph Koidu Processing plant were sorted in secured glove boxes and the diamonds classified using round aperture DTC sieves. The plant bottom cut-off size was 1.25mm. The proportion of gem quality stones is unusually high, with 99% gems at Lando A, 99% gems at Lando B and 98% gems at Kundu.
  • Geophysical Surveys Koidu Holdings contracted leading Canadian geophysics instrumentation manufacturer, Phoenix Geophysics Limited, to undertake an Audiofrequency Magnetotelluric (AMT) survey at the Koidu Kimberlite Project in March 2007. This method has been applied successfully in kimberlite exploration in Russia (Arkangelsk and Yakutia) and in Canada. The results obtained from Koidu prompted the Company to extend the survey to the Tongo Field Diamond Project, to test the effectiveness of the technique on the narrow Lando and Kundu dyke zones between the bulk sampling sites and to investigate the area around the Peyima Blow.
  • Geophysical Surveys Drilling targets were selected from the Audiofrequency Magnetotelluric survey conducted by Phoenix Geophysics and a follow-up ground magnetic geophysical survey was recommended and completed by Remote Exploration Services (Pty) Ltd in March 2010.
  • Kimberlite Types Kimberlite Type 1: Darkish, blue-grey, inhomogeneous, poorly sorted, olivine macrocryst and xenolith rich kimberlite . The mica rich groundmass has been completely serpentinised. Macrocryst olivines generally range from VF-VC are usually rounded, serpentinised and can be rimmed with carbonate. Olivines can make up to 10 to 15% of the rock. Xenoliths consist of angular to rounded pieces of granite or altered granite and can be up to 120mm in diameter. Trace amounts of kimberlite indicator minerals, especially garnet, are recorded. These garnets often show kelyphitic rims.
  • Kimberlite Types Kimberlite Type 2: The rock has the same blue-grey mica rich groundmass that has been serpentinised as Type 1, however it tends to be more homogeneous. Type 2 kimberlite is olivine macrocryst rich and xenolith poor. Macrocryst olivines generally range from VF-VC, are usually rounded, spherical to elongate, serpentinised and can be rimmed with carbonate. Olivines can make up to 25% of the rock. Very few, or no xenoliths are recorded within this kimberlite. Trace amounts of kimberlite indicator minerals, especially garnet, are recorded and tend to be slightly more abundant than in Type 1. These garnets often show kelyphitic rims.
  • Kimberlite Types Kimberlite Type 3: Dark blue-grey, homogenous / massive, xenolith and olivine macrocryst free kimberlite . The extremely fine grained mica rich groundmass has been serpentinised. No kimberlite indicator minerals are recorded within this unit.
  • Underground Sampling A second phase of surface bulk sampling is planned for 2012, in addition to a underground bulk sampling programme.
  • Drilling
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  • Engineering Analysis A detailed engineering analysis of the condition of the road between Koidu and Tongo was undertaken immediately after obtaining the Tongo exploration licence. Two possible routes were identified between Koidu and Tongo. The first is via Gandorhun, a distance of 124 km and the second is via Njaiama, a distance of 63 km. The shorter route connecting Kenema, Tongo, Njaiama-Nimikoro, Bumpe, Yengema and Koidu intersects the licence area at Kpandebu, through Tokpombu on to Bomi. The road refurbishment programme was carried out in three phases.
  • Engineering Analysis The route consisted of a bush track that was 3m at its widest and was used mostly by motorbikes. There were few concrete bridges, only one concrete culvert, and the rest of the swamp and stream crossings were by means of palm logs. This is a typical secondary provincial road with a compressed laterite subgrade, with the base resting directly on decomposed bedrock. During the reconnaissance survey, only one other motor vehicle (NGO Land Cruiser) was observed using the route.
  • Phase 1  27 September 2005 to 31 January 2006 10,656 tonnes of laterite hauled, dumped and graded to resurface Tongo-Kangama-Moimandu road
  • Phase 1  27 September 2005 to 31 January 2006 Widening of the 20km Tongo-Kangama-Moimandu main road to 8-10m
  • Phase 1  27 September 2005 to 31 January 2006 Installation of 11 steel culverts - Tongo-Kangama-Moimandu road.
  • Phase 1  27 September 2005 to 31 January 2006 Construction of 4m x 6m x 200mm concrete bridge at Konjo
  • Phase 2  1 February 2006 to 31 March 2006 Widening of the 20km Kangama-Moimandu-Njaima Nimikoro feeder road to 5m
  • Phase 2  1 February 2006 to 31 March 2006 Construction of 8m x 4.2m x 200mm concrete bridge at Njagbahun
  • Phase 2  1 February 2006 to 31 March 2006 Installation of 11 culverts between Kangama and Njaima Nimikoro
  • Phase 2  1 February 2006 to 31 March 2006 Resurfacing of road near Moimandu
  • Phase 3  1 May 2006 to 31 January 2007 Construction of 6m x 4m x200mm concrete bridge at Tokpombu
  • Phase 3  1 May 2006 to 31 January 2007 Drilling (356holes, 1,068m)and blasting (3,170 tonnes) of granite at Periwahun quarry
  • Phase 3  1 May 2006 to 31 January 2007 Maintenance and resurfacing of road with 16mm tailings from Koidu (4,958 tonnes)
  • Phase 3  1 May 2006 to 31 January 2007 Drill and blast rock at Norway. Other activities carried out in Phase 3 included: Resurfacing (4,000 tonnes of decomposed granite) and maintenance of 10km section of 5m wide road from Moimandu to Njaima Nimikoro Excavation of 12,000 tonnes of waste rock for road construction at Kangama Hill Pass Construction of temporary bridge at Kangama Resurfacing of Moimandu-Nimikoro road for Presidential visit Construction of bypass culvert at Tokpombu Repair of road between Venima and Periwahun
  • Phase 4  1 February 2007 to 31 May 2007 Widening from 12m to 15m from Norway Village to Moimandu
  • Phase 4  1 February 2007 to 31 May 2007 Widening from 12m to 15m Moimandu to Njalehun
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