Mining for Diamonds Worldwide Photo: Courtesy of De Beers

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No. 31 SRK Consulting’s International Focus on Diamonds Newsletter

Mining for diamonds worldwide photo: courtesy of De Beers

The Arctic of Northern Canada and Siberia, the jungles of Africa and South America, and the deserts of Southern Africa and Australia: these are the locations of today's diamond mines.

Diamonds are being recovered from host rocks and pipe geology. Kimberlite The political, social and economic primary deposits such as kimberlite can be as tough as granite or as weak as responsibilities placed on most diamond and lamproite pipes and dykes but soil; the strength can alter significantly producers require extensive and complex also from alluvial gravels and seabeds. with short exposure to moisture. impact assessment studies before mines From exploration to mine closure, the can go into production. The requirements The process of identifying a valuable variability facing today’s diamond of various regions, provinces and countries deposit and estimating that value is miner almost certainly exceeds that make the permitting process very complex. unique to diamonds; large samples might which is faced by the producer of any be required to get a reliable estimate; Profitable and safe mining of diamonds is other commodity. size, color and quality are all critical. very complex and challenging. However, The diamond itself – the simplicity of Many of the statistical and geostatistical these complications and challenges can the chemical composition – contrasts methods used for other minerals might be overcome using knowledge and sharply with the complexity of assessing not be appropriate. experience from a range of disciplines. the diamond’s value; the price for a Mining methods are as variable and complex Jarek Jakubec: jjakubec srk.com single-carat stone could vary in value @ as the product itself. Very few mining by an order of magnitude depending methods have not been used, from large on quality and market. open pits and caves, to narrow vein methods Then there is the variation of the kimberlite and state-of-the-art deep-sea mining.

Geology and diamond projects

Jarek Jakubec It is not uncommon to discover significant The knowledge of country rock geology is gaps in understanding the nature of the at least as important as the geology of the deposit during the later stages of projects. kimberlite pipe. Pit slopes, underground In many cases such gaps result in access development and mining development delays and cost overruns. infrastructure are mainly located in the Such “surprises” could be avoided if country rocks. Often, during the kimberlite geological investigations are integrated delineation program, holes are terminated into all levels of project development. as soon as they leave kimberlite. This can and does lead to erroneous interpretations In the early stages often the geological of pipe geometry because the assumed data is limited to the resource model and “country rock contact” is only a country very little is known about the country rock rock xenolith. geology or pipe contact zones. In order to reduce the risk of selecting the “wrong” For a mining operation to be successful, it mining method or raising “unrealistic” must bring fundamental and applied expectations for the particular mine science together. The mining engineer design, it is important to understand all must understand the importance of aspects of geology, such as regional geology, mineralogy and petrography and structural geology, kimberlite pipe as well the geological scientists must be familiar as country rock geology. with project development from the exploration stage through mine design and Structural geology is fundamental. In the operation to mine closure. Canadian Arctic, where many kimberlites are being discovered under the lakes, Jarek Jakubec: [email protected] understanding of structures can have a major impact on the mining concept and strategy.

The pipe emplacement mechanism could influence pipe size and geometry, internal structures, rock mass competency and the character of the pipe contact zones. 3D visualization of pipe geology All these parameters could directly affect helps with fundamental decisions on mining strategy and layout pit wall stability, underground mining method selection, dilution, treatment plant process, or dewatering strategies.

The petrology and mineralogy model could be crucial to factors in a diamond resource estimate but also in diamond damage and liberation, slope stability of the pit wall and underground excavation, support design, mine safety (mudrush risk assessment), mine dewatering and environmental issues. Characterizing the clay provides important clues to the weathering susceptibility of the kimberlite rock types. editorial

Contribution of structural geology

Chris Lee In most mineral systems, applied structural geology is about the early stages of mine design, mine understanding “pathways.” Pathways include the crustal scale planning and mine safety, and its plumbing systems that facilitate the emplacement of kimberlitic application to groundwater studies further extends its relevance magmas, as well as the pipe scale fault/fracture networks that for mine closure and remediation. control groundwater flow and alteration during and after The maximum benefit of structural analysis emplacement. Understanding these pathways is realized when it is introduced early, can profoundly affect the during the initial assessment success of diamond stages of a project, when it can projects at all stages. be used to considerable Today’s common diamond advantage in focusing exploration tools consist subsequent investigations, and primarily of airborne geophysics thereby saving significant amounts of and quaternary geology (soil both time and money. sampling). In many cases, both Structural interpretations have techniques – whether used been successfully conducted by together or in isolation – have SRK on several Canadian proven to be highly diamond projects. successful means of locating kimberlites and diamonds. Chris Lee: [email protected] However, where kimberlites have no distinct magnetic signature or traceable dispersion train, understanding the crustal Successive filtering of architecture and its structural- geophysical data, combined kinematic evolution can provide with geological knowledge, valuable insights into their results in a reliable structural geology location and distribution. Using image. existing aeromagnetic data, crustal scale geology and the tectonic history of a given area, structural analysis can help identify favourable sites for pipe emplacement.

Effective management of ground stability and groundwater issues are two critical elements underpinning the success of any mining operation. Structural analysis of faults and fracture systems outside and within the kimberlite can help predict zones of instability and groundwater risk. Groundwater flow is not only an immediate impediment to development, it can also lead to progressive weakening of the groundwater pathways over time. Structural geology is an important tool in

Understanding micro structures often provides insights to large-scale structural geology

Unique aspects of waste rock management

Open pit diamond mines typically have tailings at diamond mines from waste rock • Natural high high stripping ratios and therefore result in and tailings at metal mines are described weathering generation of large volumes of waste rock. as follows: susceptibility of As a result of experience at other types of many kimberlites • Kimberlite pipes are emplaced rapidly mines throughout the world, the expectation (a combination at relatively low temperatures. Unlike from regulators and the general public is of physical most metal deposits, this results in little, that the waste rock can generate severe and chemical if any, alteration of the surrounding country environmental impacts through oxidation degradation) leads rock. Unless these rocks are mineralized of sulphide minerals, the worst result of Kelly Sexsmith to rapid exposure as a result of another process, the which can be acid rock drainage (ARD). of any sulphide sulphide minerals that can have minerals present in the rock, and SRK’s Vancouver office has been involved negative environmental impacts are consequently rapid rates of sulphide in pre-mine and operational geochemical typically very rare. oxidation. The presence of magnesium in characterization of waste rock at several • Kimberlite itself is comprised of a the rock supports high sulphate new diamond mines in Canada (Ekati complex suite of mantle-derived concentrations possibly resulting in a need Diamond Mine,™ Diavik™ Diamond Mines magnesium silicate minerals along with to manage elevated total dissolved solids Inc., Jericho Project and Victor Project), carbonate minerals. Sulphide minerals are (TDS) in seepage and runoff. and is at the forefront of demonstrating to often present in trace amounts, and are stakeholders in the mine permitting An understanding of these properties is more likely to be associated with the process the importance of understanding the key to developing waste rock country rock entrained in the kimberlite the geochemistry, mineralogy and management plans that meet the specific during emplacement, or by collapse of the geological model for emplacement of needs of the diamond mining industry. crater. Due to the relatively high amount of kimberlite, and how these features affect carbonate and low amounts of sulphide, Kelly Sexsmith: ksexsmith srk.com the long term chemical stability of the @ kimberlite ore and tailings are not likely to Stephen Day: sday srk.com waste rock and tailings. Some important @ generate ARD. features that distinguish waste rock and

General view of Panda open pit at the Ekati Diamond Mine™ with waste rock storage area on the right

Indicator testing Kimberlite weathering – of kimberlite complex issues weathering

Jarek Jakubec SRK is using a simple qualitative “accelerated” weathering test to establish the degree of weathering of various kimberlites. The core or rock lump specimens are subjected to wetting and drying cycles and the deterioration of the core after each cycle is documented and photographed. The results are then compared to known kimberlites from other mining projects, which allows the impact on slope design or support requirements to be assessed. The two photos below show the extent of the deterioration of various kimberlitic rock types after several wetting and drying cycles. Note that some kimberlites completely disintegrated while others stayed intact. Although the test does not Kimberlite weathering can cause rapid pit slope deterioration provide quantitative results, it can be performed on site, quickly and on large quantities of samples. “It is not a rock” somebody at a present in the rock matrix. If clays from the diamond mine said about kimberlite. Of smectite group are exposed to moisture or Jarek Jakubec: [email protected] course, technically speaking, he was not – even worse – to wet and dry cycles, right, but sometimes I wonder if we really they swell and disintegrate the rock matrix, are dealing with rocks. The physical dramatically reducing the strength of the properties of kimberlite can be extremely rock mass. The stability of excavations, variable and geotechnical issues of the supportability of the rock mass, and kimberlite pipes very complex. Failure to trafficability are all in jeopardy. To combat characterize such issues could have kimberlite deterioration many underground significant consequences for mining diamond operations apply sealant to projects. prevent moisture from entering the exposed rock. Failure to do so can result One of the fundamental geotechnical in rapid tunnel deterioration. Preventing issues to consider in selecting the mining The kimberlite core samples above are kimberlite weathering could pose method and design is the strength and shown below after only 3 wetting and particular challenges in the Arctic where deformation characteristic of the rock drying cycles – many with extensive low temperatures or condensation could deterioration mass in which mining takes place. Not prevent effective application of most only can various kimberlite rock types sealants. have variable properties, such properties can change rapidly with time. Most It is important, therefore, to characterize kimberlites fall into the category of weak the weathering susceptibility of the to moderately strong rocks. In the context various kimberlite rock types in the early of mine design this would not pose a stages so these factors can be built into challenge. The problem arises if kimberlite the mine design to forestall a “surprise” loses strength within days of exposure. during the development.

This can happen if the “wrong” clays are Jarek Jakubec: [email protected]

Coarse kimberlite rejects at Ekati Diamond Mine™

The environmental effects of weathering that results from processing kimberlite. are leached by and leaching of kimberlite recently In 1999, routine monitoring of shallow contact with natural, came under the microscope with the pools along the toe of the CKR pile strongly-acidic soils. successful development of diamond mines showed that drainage from the pile To counteract this, in northern Canada. BHP Billiton and resembled acid rock drainage, even BHP Billiton now Diavik™ Diamond Mines Inc. though testing of the CKR had clearly designs its waste (a subsidiary of Rio Tinto) operate mines shown that the potential for acid kimberlite storage located in a pristine arctic wilderness area generation was negligible. The drainage areas so that the where lake water is exceptionally pure and was also quite different from process foundation does not Stephen Day highly sensitive to impacts. SRK’s water entrained in the CKR. come in contact Vancouver office is involved in the with acidic soils, and Identifying the source of elevated environmental assessment, permitting and so that the concentrations of the total dissolved development of these mines. extremely cold conditions in the region solids in the water was a high priority. are harnessed to freeze the soils. At BHP Billiton’s Ekati Diamond Mine™, BHP Billiton’s engineers design waste SRK geochemists Stephen Day and management plans, and the company Stephen Day: [email protected] Kelly Sexsmith worked closely with mine had applied for permits to mine several staff to evaluate the unusual weathering new kimberlite pipes in the area. behaviour of coarse kimberlite rejects Through detailed investigations, SRK and (CKR) – the fine gravel-sized material BHP Billiton have determined that CKR

SRK’s Kelly Sexsmith sampling seepage from coarse kimberlite rejects at the Ekati Diamond Mine™

Diamond resource estimation

The estimation of the resource content range from a few US$ per carat to in kimberlite pipes – primary host rocks over US$10,000 per carat. Normally for diamonds – entails a number of a parcel in the order of 5,000 carats is aspects that are unusual, compared required and a valuation-per-size class is Tinus Oosterveld with the resource estimation for other requested for valuation. This information is minerals. Diamonds occur as discrete used to model the value per size class and particles, each with its own size and this information together with the expected quality. Combination of highly variable diamond size frequency during production values per unit-weight and relatively low is used to estimate revenue. occurrence makes sampling and Knowledge of statistical and geostatistical resource estimation very complex. methods combined with sound practical In kimberlite, diamond sizes range from experience is essential for realistic in-situ dust-size particles to diamonds larger estimates. To correctly evaluate the than 100 carats per stone. The real value recoverable resource, the geology, mining of diamonds lies in particles larger than method and process plant type has to be approximately 0.1 carat per stone; taken into the equation. Jarek Jakubec smaller diamonds are normally not and Mike Michaud from SRK Canada are recovered. The diamond recovery is working closely with Tinus Oosterveld, related to the characteristics of the the world’s leading authority on diamond treatment facility in terms of cut-sizes, resource evaluation, on resource crushing sizes and re-crush sizes, and estimates for a North American client. these characteristics are often different Tinus Oosterveld: tinus global.co.za in a sampling treatment plant, a bulk-test @ treatment plant and a production treatment plant. Diamond Recovery Model

Diamond-size frequency analysis is 100 an important tool that helps 90 Bulk 1 compare the recovery in different 80 LDD 1 treatment plants and relates it to 70 revenue obtained. The diamond- Model 60 size frequency is normally obtained by sieving the diamonds on round 50 aperture sieves. The tools used for 40 Grade, CPHT interpreting diamond-size 30 requencies are cumulative carat 20 plots on logarithmic probability paper. The distribution of diamonds 10 in kimberlite is close to log-normal 0 and a plot on logarithmic probability 0.01 0.10 1.00 10.00 paper shows as a straight line. Average Size, CTS/STN Deviations can signify recovery Bulk sampling gives a better efficiency problems. Another graph of representation of larger stones. grade-by-size plots can be used to compare treatment plants and to check Large Diameter Drillhole (LDD) for recovery efficiency. provides a better sample throughout the entire orebody, but a limited Another aspect of diamond resource representation of larger stones. estimation is diamond value. The The most accurate model is based value of individual diamonds can on a combination of both methods. photo: courtesy of De Beers

Permafrost and mining Diamond mining in an Arctic context

While the impact of permafrost on soil stability is well documented, there is a relative shortage of information in the public domain dealing with open-pit or underground mine design criteria for orebodies located in permafrost. SRK Canada has been involved in several mining projects situated in the high Arctic where the issue of permafrost had to be evaluated.

The Nanisivik underground mine is located in Nunavut on northern Baffin Island approximately 750 kilometers north of Steep slopes of Aikhal diamond mine are only feasible because of permafrost conditions and good blasting practices the Arctic Circle. The lead/zinc/silver orebody was mined partly as a room and pillar operation. SRK helped to develop a mine layout that would take the Canada’s SRK team is involved weak. A number of mining challenges strengthening effect of permafrost in development of diamond projects in must be faced in the mine design. But on the rock mass into account. the Arctic for several reasons. These most important the differences in rock include experience with kimberlite mining mass must be recognized and carefully Open-pit diamond mines located in in Southern Africa and Russia, worldwide assessed. Add the harsh Arctic Siberia also illustrate the impact of experience with caving and non-backfill environment and the location of most permafrost on the rock mass. Most of methods typical for underground diamond diamond-bearing pipes under lakes and the open-pit slopes are steeper than operations, and extensive experience with you have some idea of the complexity of those located in “warmer” climates. operations in the far North. the mining difficulty. Although good blasting practices are still required some of the pits could achieve Primary diamond resources in the Arctic SRK’s experience with Arctic diamond slope angles of 60 degrees and more. are mainly associated with kimberlites. projects includes: Kimberlite rocks are known for the The Snap Lake project. The first diamond Clearly the effect of permafrost needs to variability of their geological, chemical project to mine a shallow-dipping, be taken into consideration when and physical properties that distinguish diamond-bearing kimberlite dyke on designing an open-pit or underground them from other rocks encountered in a large scale. Most diamonds mined mine. The economic benefit, however, underground operations. Kimberlites from primary sources have come from cannot jeopardize safety, which should be can weather extremely rapidly (some kimberlite pipes; kimberlite dyke mining the highest priority of the mining project. operations must proceed without water); in South Africa is limited, such dykes they can “absorb” blasts that make them Jarek Jakubec: [email protected] dip steeply and the operations are difficult to break; they can be extremely

Diamond mining expert: Diamond mining in an Arctic context Jarek Jakubec

Chris Page Jarek Jakubec Jarek Jakubec, principal engineer with SRK Canada, is based in the Vancouver office. He has more than 18 years of operational and consulting experience in geology, rock mechanics and mining; his personal focus areas are block caving and diamond mining.

After spending eight years in geology and mining in Europe and Canada, Jarek joined De Beers Consolidated Mines in South Africa in the capacity of senior geotechnical engineer. Soon he moved to Botswana, where he was given responsibility for leading the Geotechnical Section for large open-pit diamond mines. “Botswana produces approximately one-third of the world’s diamonds by value,” says Jarek. “And it was exciting to be involved with such an important diamond producer.” Besides geotechnical engineering, he was also involved in the geological modelling of diamond pipes and participated on several research studies, such as kimberlite weathering effects on mine design. Steep slopes of Aikhal diamond mine are only feasible because of permafrost conditions and good blasting practices Jarek joined the SRK office in Vancouver in 1997 and started actively promoting consulting services for the diamond small-scale. The Snap Lake dyke in the BHP Billiton. Most of these projects are industry. He has been involved in a wide Canadian Arctic is located mostly under open pits converting to underground as variety of underground and open-pit a large lake at depths ranging from 100m the strip ratio increases. Many are likely to projects, as well as several training to 500m. be mined by non-backfill methods, a programs for clients’ geotechnical and major departure from typical operations The Jericho project. A comparatively small engineering staff. His wide experience in Canada. Plans for the Ekati Diamond with mining diamonds led to his being kimberlite pipe on dry land, Jericho is ™ Mine are well advanced; their first located in permafrost, which, in fact, may chosen as project manager on the underground operation at Koala North produce better ground conditions. feasibility study for the Jericho Diamond uses the “open benching” mining method. It will start as an open pit and convert to project in Northern Canada. He has also “open benching” at depth. Underground operations in kimberlites participated in diamond resource present challenges that can be managed evaluation, with Tinus Oosterveld, the The Victor project. Victor pipe already as long as the technical concerns are world’s leading authority in the field. presents some complex issues for mining recognized and evaluated correctly. in the North; extensive dewatering is Over much of his professional career, required and some challenging materials Jarek has had the opportunity to work must be excavated from this large open- on exciting diamond projects; this has Jarek Jakubec: jjakubec srk.com pit operation. @ allowed him to visit most of the diamond Dr Chris Page: [email protected] producing mines around the globe, ™ The Ekati Diamond Mine operations. including those in Siberia, southern Includes several underground projects for Africa, Brazil, Australia, and Canada.

Jarek Jakubec: [email protected]

Diamond mining at great depth

Premier Mine near Pretoria, South Africa, group. Dr. Dennis Laubscher, the world’s Correct assessment of the stress produced the world’s largest diamond leading expert on block caving, is also conditions for the various strategies will gem – the famous Cullinan – which involved in the mining aspect of the project. be critical for the successful development weighed 3,106 carats. Since operation of the undercut and production horizons. Underground mapping and additional started in 1902, more than 113 million Knowledge of the water regime is drilling data provided a basis for the carats of diamonds have been mined. important, not only from the operational comprehensive rock mass characterization point of view but also to investigate The current plan is to replace existing and geotechnical assessment. Based on the potential risk of mudrush and production with operations at deeper this assessment a 3D geotechnical domain support deterioration. levels through two new vertical shafts model was built in Gemcom software. that will provide ore to a new treatment The model was then converted to a block Jarek Jakubec: [email protected] facility built on the surface. This would model to set up the FLAC numerical model. significantly increase the processed Calibrating the numerical model to tonnage. The extension would take mine existing conditions will help us workings down to more than 1,000m understand rock mass behavior below the surface. That would make it at greater depths. The model one of the deepest underground diamond can then be used to simulate mines in the world. different mining scenarios and layouts. SRK Consulting is part of the multidisciplinary team that is helping Dr Loren Lorig (Itasca), Alan De Beers with its geotechnical and Guest (De Beers), Jarek hydrogeological investigation for the Premier Jakubec (SRK) and Dr Denis Centenary Cut project. Jarek Jakubec from Laubscher – members of the Vancouver office and Fred Harvey from the multidisciplinary team the Johannesburg office are working along for the Premier Centenary with experts from the HCItasca consulting Cut project

Premier is one of the deepest diamond mines in the world

SRK Australasia and the Argyle diamond mine

The Argyle mine yields more diamonds than any other mine in the world - 30 million carats/annum

Argyle Diamond Mines Pty. Ltd. own and footwall of the AK1 resource, to undertake SRK has provided all operate an open-pit diamond mine in the a study into mining of the Southern Tail engineering design Kimberley Region of northern Western resource by underground stoping input to a detailed Campbell Baird Australia. The AK1 ore body consists of a methods and then develop it to the engineering level. volcanic intrusion of Lamproitic tuff and detailed engineering stage. Unlike the diamond projects in the magmatic Lamproite. SRK Consulting was Several mining scenarios were developed Canadian Arctic, the AK1 orebody will face commissioned to undertake a pre- and evaluated involving sublevel caving, many ventilation challenges as a result of feasibility study to assess the economic block caving and a combination of both heat load from groundwater and impact of viability of extraction of the orebody by mining methods. The individual scenarios extreme tropical climate conditions. The underground caving methods. also included various ore delivery options, ambient air temperature and humidity Studies were first undertaken to gain an such as staged and trim lift conveyor and levels at Argyle are high and cooling of the understanding of the geotechnical shaft. air before circulation underground will be characteristics of the ore, the surrounding essential. With SRK’s help two options were rockmass cavability and ultimate selected for full feasibility study, which is Campbell Baird: cbaird srk.com.au fragmentation during caving. The study @ scheduled for completion in 2004. It was then investigated alternate mining, material also decided that an early exploration handling and ventilation options. As a part decline should be developed to allow of the study, SRK were also asked to access into the AK1 orebody at depth. review mass stoping methods for the

SRK works with De Beers in Botswana

The Orapa diamond mine is located in Orapa A/K1 kimberlite was For such a large pit, the slope central Botswana, approximately 220km discovered in 1967, and since angle design has enormous west of Francistown. The climate is semi- 1971, more than 121 million economic consequences. As a arid; temperatures range from above 45°C carats have been extracted. result, every aspect affecting the in summer to below 0° at night in winter, The bottom of the open pit open pit must be examined to while the annual rainfall averages less currently lies 150m below minimize the stripping ratio and than 450mm. The morphology of the the surface, at 810m above meet safety requirements. surrounding area is flat, apart from a mean sea level. To date, all SRK has worked on the few low hills and ridges; it supports low mining faces of Cut 1 are Peter Terbrugge slope design and optimization savannah-type vegetation. confined within the kimberlite at Orapa for 20 years and pipe boundary. The plan is to The A/K1 kimberlite pipe, with a surface is currently evaluating the effect of exploit area of 118ha, is the largest of a group of weathering on mudstones in the pits and the Orapa pipe by the open-cast mining more than 60 known kimberlites in the area. the need to pre-treat them to achieve method until 2030, increasing the Included among these are Orapa A/K2 steeper overall angles and save on rate of production as number 2 plant and Letlhakane D/K1 and D/K2 pipes. stripping costs. is commissioned. Ultimately, the pit Like A/K1, they are mined for diamonds. depth will extend more than 500m Peter Terbrugge: [email protected] below surface.

Orapa A/K1 diamond open pit is located in a semi-arid region of Central Botswana

SRK Offshore

Undersea mining unit used to extract sediments from the sea floor

Since 1998 SRK has been developing SRK uses the prospectivity rating and the (cts/m2) by using methodologies for the exploration, success rates of exploration and indicator kriging to Alwyn Annels evaluation and exploitation of offshore exploitation programs to estimate the determine the diamonds. To aid exploration we have resource potential of each feature type probability of zero identified eight different types of “feature,” and the global potential for all the licence values and then combine the results with which can be detected by geophysical areas held. The rating only indicates the kriged planar grades. Block modelling was survey. On the continental shelf off South potential value of the licence areas, not the constrained within digitized areas, whose Africa and Namibia, sediment-filled resources from which mineable reserves limits were defined by sampling with the depressions on the sea floor bedrock are could be determined. Wirth drill and Vibrocorer, and through known to contain diamonds and range geological interpretation based on Developing a resource evaluation from open basins to narrow channels and comprehensive geophysical data. methodology, which relies on a strong gullies. Each feature is assigned a understanding of geology, was SRK’s next The method proved very successful in prospectivity rating based on its proximity goal. We selected one that company predicting the distribution and grade of to diamond source, the ease of transport geologists could use with current stand- potentially economically viable diamond and potential for entrapment, concentration alone software and without the need for a concentrations without resorting to and preservation of diamonds. The rating deep understanding of statistical theory. statistical methods remote from geology. also reflects operating experience and the The method identifies “negative” sample Failure to take valid zero grades into presence of positive sampling results. information reflecting the margins of account in the past had produced Prospectivity may be downgraded if diamondiferous sediments, the apparent misleading resource estimates, particularly water and sediment depths fall outside lack of internal continuity of grade for deposits considered economically acceptable ranges for current mining (reflecting sample size) and “technical marginal using current mining technology. techniques. This classification system led failures.” Once these technical failures are naturally to the development of a sampling Dr Alwyn Annels: aannels srk.co.uk removed, we estimate the planar grade @ strategy for each feature type.

Due diligence at Archangel, Russia Groundwater investigation at Victor

SRK, assisted by a representative from Société Générale de Surveillance S.A. (SGS), took on due diligence of drilling, drill core sampling, processing and diamond recovery at a diamondiferous kimberlite pipe in northwest Russia.

The pipe, located about 100km NNW of Arkhangelsk, is only accessible by semi- Mike Armitage submersible tracked vehicles, travelling over waterlogged logging roads and large peat bogs. This made the logistics of the drilling operation very difficult, and the midsummer insects Winter logistics… one challenge of working in cold climates made the fieldwork extremely taxing.

A SRK senior geologist travelled to the site to supervise the entire process of drilling SRK has been involved at the De Beers collection points and sampling. He accompanied the Victor Project in the James Bay region of away from the Michael Royle sample as it was transported to the northern Ontario for the last five years. kimberlite body Pomorye kimberlite processing plant, kept Initially, the scope of work covered the rock measured the the core sample under constant mechanics of the pit wall area. However, in well's effects and its potential impact on supervision during processing and partnership with HCItasca a preliminary the local water courses. Geochemical maintained the sample in strictest security groundwater investigation was integrated monitoring has been employed to model at the processing facility and during with this program to assess pit dewatering environmental discharge and to comply sorting of the concentrate. Finally, the and water treatment requirements. In the with environmental permitting. diamonds recovered from the concentrate first year, deep geotechnical drillholes were Conventional wells were planned to were described, weighed and hydraulically tested (packer tests) and dewater the main pit area. However, a independently verified by SRK and SGS. instrumented using grouted vibrating wire deep glacio-fluvial sediment filled piezometers and thermistors to collect data According to project director Mike depression posed problems that had to be on groundwater flow to the pit area. Next, a Armitage “It was extremely important that evaluated by several unconventional phased program was carried out using we provided a completely independent methods: by “freeze-wall” technology using large-diameter airlift tests, followed by two and impartial assessment of the deep thermosyphons and deep cut-off wall seasons of dewatering and well-pumping competence of the drilling, sampling and construction. Both systems are currently tests. As the scale of the investigation processing operations, as this enabled us used on other projects, but not to the increased, the monitoring system design to confirm that the highest standards, depth required at Victor. was expanded to collect data on the methods and levels of security were being effects of local lithology and large scale Dewatering system design will play an employed by our client and it’s joint structures over a larger area of impact. important role in the economics of the venture partner and that the reported mine due to the significant costs for diamond grades and qualities could In 2003, two dewatering wells were tested providing power at the site. This aspect therefore be relied upon by shareholders separately, for 10 and 30 days, to assess applies to most of the Canadian diamond and potential investors.” large scale dewatering impact and projects, and to all of the northern mining potential effects on the local river system Dr Mike Armitage: marmitage srk.co.uk projects SRK is involved with. @ respectively. A significantly enhanced monitoring system with numerous Michael Royle: [email protected]

Underground diamond mining in Canada

Following South Africa and Russia, kimberlite mining in the Arctic, where a and across Canada has become the latest country project has to deal with a unique set of the kimberlite pipe for to open an underground diamond mine. mining conditions in a harsh environment. slot access, stope Jarek Jakubec BHP Billiton’s Koala North is being drilling and production The mine is accessed from a ramp developed as an open-benching, mucking. Due to the geo-mechanical and developed at the surface. Because of mechanized, trackless operation. weathering characteristics of kimberlite, the presence of permafrost, all of the Dr Chris Page and Jarek Jakubec from development and production blast hole granitic country rock is drilled using a SRK’s team in Vancouver helped BHP drilling must be completed dry. brine solution. Production access routes Billiton’s engineering team select the branch off the ramp at regular intervals SRK is proud to be involved, together with mining method and basic design criteria. to reach the kimberlite pipe. These levels BHP Billiton’s team of engineers, in Although the method was successfully provide access for stope production, identifying and solving some of the used at several De Beers diamond exploratory diamond drilling, and challenges of mining in the Arctic. operations in South Africa, it has never mining infrastructure, including sumps, been tested in an Arctic environment. Jarek Jakubec: jjakubec srk.com refuge bays and electrical installations. @ Consequently, Koala North will serve as a Production tunnels are developed into learning experience for underground

Development at Koala North – the first Canadian underground diamond mine

SRK UK’s Alluvial diamond reserves Bruce Evans in areas of artisanal mining

ruce Evans together alculating the value of alluvial diamond B C Allan McCracken with Neal Rigby and resources and reserves is a challenge in Roy Barfoot, started normal circumstances, considering the company’s UK variations in grade, distribution, stone size, consulting practice in diamond value and recovery constraints. 1988 where he Still, good techniques have been pioneered due established, based on reliable sampling diligence of mining methods, an understanding of geology, Bruce Evans projects for London Banks and Stock statistical evaluation and sound practical Exchange Listings, a business that has experience. But when artisanal miners grown in scope and size and spread to have previously worked the deposit, several other SRK offices. especially over many decades, all of these variables need close attention as well as He has many years of experience in an estimation of the amount of the deposit hands-on operation, project evaluation and implementation at senior levels they have extracted. with Gencor (now BHP Billiton), both in Artisanal mining is usually more expert than South Africa and other countries on many would expect and can easily account four continents. As CEO of Gencor’s for 50% of the grade worked. This, Gold and Uranium Division, he headed Central African artisanal miners a 100,000-employee business with however, may represent far more than 50% fourteen listed mining and process of the value of the stones as the larger, plant companies, producing 100 tons better quality stones are mined preferentially. the deposit, the remaining resources and of gold a year. reserves can be determined by classical SRK Consulting has evaluated several methods. However, exploration sampling such diamond deposits, each with their Bruce specializes in interpreting in active artisanal mining areas needs a own individual features, and has developed orebodies, their mineability, overall mine higher degree of security and vigilance. a series of relevant rules and tests to apply. feasibility and mining economics, Co-existing with artisanal miners requires especially in gold, base metal Good maps and recent aerial photographs specific environmental considerations, and underground mining and alluvial the project must recognize the conflict of diamonds. He has been involved in alluvial are essential along with local knowledge diamond sampling, mining and economic and understanding of the mining context. interests that exist and work towards assessments of properties in the Congo The extent of artisanal exploration and accommodation at an early stage. and Guinea and in the statistical and mining has to be established and the While there are challenges in mining in such geostatistical analysis of a diamond artisan’s cut-off grade estimated. In this areas, the projects are potentially viable. mining property in West Africa. context, a good history of the water table SRK has been able to obtain reliable and its movements and whether the miners estimates that should achieve the same He led a multi-disciplinary team of six have used pumps, is very important. experts in performing the technical- bankable status as any other project. economic due diligence analysis of a Once it is possible to estimate the Bruce Evans: [email protected] significant diamond pipe in Angola. percentage depletion in different areas of Allan McCracken: [email protected] Bruce has consulted extensively on offshore diamond deposits and the mining of them, in particular for Namibian Diamond Corporation during its heyday. SRK For more information, visit us at www.srk.com seconded him as chief operating officer as the company depleted its known reserves and struggled unsuccessfully to catch up on its exploration and feature definition backlog.

Bruce Evans: [email protected] Issue No. 31

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