Following positive results from the Phase I bulk sampling programme at its BK16 kimberlite project in the Orapa Kimberlite Field of Botswana, Tsodilo Resources, listed on the TSX-V, is to undertake a second – and much bigger – phase of bulk sampling at the BK16 site.
The company reports that a renewal application for Prospecting Licence 369/2014 has been filed with the Department of Mines (DOM) at the Ministry of Mineral Resources, Green Technology and Energy Security (MMGE) in Gaborone. The renewal application is for a two-year period and the area contains the company’s BK16 kimberlite project. The centerpiece of the renewal application is the Phase II surface bulk sampling.
The BK16 pipe was discovered by De Beers in the 1970s using soil sampling techniques, airborne magnetics and ground magnetic surveys. Tsodilo’s involvement with the project dates back to 2014 when it acquired the prospecting licence over the kimberlite.
In January this year, Tsodilo presented encouraging modelled grade and diamond value reports for the BK16 kimberlite from its Phase I sampling programme that consisted of a 2 077 tonne Large Diameter Drilling (LDD) bulk sample. Phase I sampling was designed to obtain an initial determination of the quality and value of the BK16 diamonds.
The Phase I bulk sample successfully demonstrated the potential of the BK16 kimberlite to host high value diamonds between US$281 and US$792 per carat and also confirmed the presence of Type IIa diamonds consisting predominantly of D colour stones. Moreover, it confirmed the potential of BK16 to host large special stones of +10,8 carats with size frequency distribution analysis indicating that 2 % to 5 % of the total carats might be greater than 10,8 carats (specials).
According to Tsodilo, this size frequency distribution (SFD) compares favourably with Lucara’s Karowe mine (AK6) production of specials at 5,6 % and 6,8 % in 2017 and 2018 respectively.
Tsodilo says the positive results from the Phase I programme justify moving on to Phase II. The objective of this is to increase the number of carats significantly by processing a far larger sample which will lead to an increase in the certainty of the grade and diamond value.
The Phase II programme will extract 20 000 tonnes of kimberlite to obtain 800 to 1 600 carats of diamonds and will significantly improve the understanding of the grade of the deposit in carats per hundred tonnes (cpht). It will solidify further the accuracy of the high diamond value in US$ per carat and further confirm the presence and quality of the Type IIa diamond population and the presence of larger stones. In addition, it will allow an inferred resource to be defined and further refine the accuracy of the economic fundamentals of the project to move towards detailed feasibility studies and ultimately mining.
Since the completion of the Phase I programme, Tsodilo has been developing the Phase II programme with third parties to ensure that sufficient carats are obtained in the most cost effective and viable manner. Phase II will be optimised for size of sample over geographical dispersion. To achieve this, Tsodilo has decided to move away from LDD bulk sampling to a surface bulk sample method to obtain the required volumes as efficiently as possible. The company has determined that a surface bulk sample of a boxcut-style design will be the most economic and viable option for Phase II and, to this end, a number of contract mining companies were contacted to quote on surface bulk sampling of 20 000 tonnes of kimberlite.
Tsodilo says the envisioned Phase II surface bulk sampling programme constitutes standard industry practice for diamond exploration of kimberlites such as BK16 to gain enough carats for an effective economic analysis. A similar style of surface bulk sampling was employed by the Boteti Joint Venture (De Beers Prospecting and African Diamonds) during their Phase II exploration of the AK6 kimberlite in 2006.
That Phase II surface bulk sampling recovered 19 467 tonnes of kimberlite which – when combined with the LDD sample drilling of 6 045 tonnes – formed the basis of the AK6 resource statement and positive feasibility study in 2007. The positive diamond recovery results obtained from these samples led to a mining licence application being filed in 2008 followed by the development of the Karowe mine, which was commissioned in 2012 by Lucara Diamond Corp.
The Phase II bulk sample design for BK16 will be a basic small and shallow boxcut-style bulk sample; 25 m of over-burden will be stripped to expose the kimberlite below resulting in a depth of the boxcut of 30 to 35 m.
Tsodilo has held advanced discussions with Trollope Botswana for the purpose of undertaking the boxcut-style surface bulk sampling programme on behalf of the company. Trollope is the main contract mining company at Karowe, which is located 25 km south-west of BK16.
Tsodilo believes Trollope has the experience and expertise to conduct this surface bulk sample in an efficient, safe and professional manner. The company is also exploring the possibilities of using continuous miner type technology and is in discussions with Vermeer Corp on the viability of this option.
Tsodilo is in the process of finalising the bulk sample design plans and these – along with a rehabilitation design – will be verified by an independent mining engineer prior to final consultation with and approval by the DOM.
Photo courtesy of Tsodilo
