Modern Mining October 2019

DIAMONDS

Progress at Tongo diamond project on multiple fronts

Project Management (PPM) of Johannesburg in April 2019. Other key contributors to components of the FEED Study were MPH Consulting, Z-Star Mineral Resource Consultants, SRK Consulting and Datamine. Based on the reserves only model from the FEED study, the Tongo Mine Development is expected to deliver a mining operation with an initial eight-year life. Total diamond production of 1,1 Mct is forecast with a peak diamond production of 260 000 carats in Year 5. A US$222/ct realised price is expected while the forecast unit opex is US$115/ct. The estimated capex for the project is approximately US$29 million. Mining will be exclusively by underground meth- ods with single portal access to Kundu and Lando being provided from the boxcut, which is located approximately midway between the two kimberlites. The selected mining method is traditional shrinkage stoping (with an 85 cm stoping width), a method commonly used in similar kimberlite dyke mining operations in South Africa. The single decline to Kundu and Lando will com- mence with a 6 m x 4 m portal entry and continue at the decline slope angle of 8 degrees for a distance of 149 m, whereafter it will split into two separate declines of 4 m x 4 m dimensions towards Kundu and Lando respectively. The joint decline will take approximately four months to develop and equip before the split. Thereafter, the 4 m x 4 m declines will continue at a slope of 8 degrees and spiral down to Level 5 (48 masl) which is the basis of the current mine plan.

ASX-listed Newfield Resources has reported excellent progress on its Tongo diamond project (Tongo Mine Development) in eastern Sierra Leone. The drilling, blasting and excavation of the boxcut which will give access to the planned underground mine has been completed and Newfield has also concluded a lease agreement for mining equipment. In addition, a new drilling programme has begun with the aim of expanding the project’s resource.

T he Tongo Mine Development combines kim- berlite dyke-hosted diamond resources on two adjacent mining licences that cover over 134 km 2 and host 11 identified diamondifer- ous kimberlites. It is subject to a Tribute Mining Agreement between the two mining licence hold- ers, these being Newfield’s subsidiary company, Sierra Diamonds Limited, and Octéa Mining’s sub- sidiary company, Tonguma Limited. Newfield has full management and operating control of the combined Tongo Mine Development. Only four of the identified kimberlites are incor- porated in the current JORC-compliant indicated and inferred diamond resource estimate of 7,4 million carats. Of this resource, a 1,1 million carat probable reserve has been declared for just two of the kim- berlites, Kundu and Lando. A FEED study on Tongo was commissioned by Newfield following its acquisition of Stellar Diamonds in early 2018. The study was completed by Paradigm

Boxcut development at the Tongo diamond project.

To complete the boxcut excava- tion, five blasts were undertaken and some 52 000 m 3 of blasted granite have been removed to the waste dump stockpile, where Newfield has recently established a crushing plant to produce aggregate for the mine construction. The boxcut is now at the elevation required based on the geotechnical studies to ensure that the portal entry for the decline to access both the Kundu and Lando kimberlites can be drilled and blasted. A consulting rock engineer has visited the site and undertaken a geotechnical study to make rec- ommendations on the required support for the boxcut and the initial

24  MODERN MINING  October 2019