JOHANNESBURG (miningweekly.com) – Mining consultant MSA has recommended a trial mining stage of one-million tons for Aim-listed Paragon Diamonds’ Lemphane kimberlite project to recover in excess of 20 000 ct and establish a mineral resource estimate, following the formal conclusion of the project’s bulk sampling programme.

This strategy was in line with the objectives of the project’s recently awarded mining lease.

"The results of the bulk sampling programme have confirmed the potential for Lemphane to contain large valuable diamonds. It has also demonstrated that the processing of larger volumes of kimberlite will proportionally improve the recovery of additional larger diamonds. These recoveries can then be used to determine representative grade and value estimations for Lemphane,” Paragon chairperson Martin Doyle commented.

He added that the proposed Stage 1 production of one-million tons over two years had been designed with this objective in mind.

During the bulk sampling programme, the Lemphane project’s South domain, which comprised about 65% of the area of the kimberlite pipe, had a sample grade of close to 2.2 carats per hundred tons (cpht) based on a total bulk sample of 10 586 dry tonnes of kimberlite from four sample pits.

The North domain, which comprised about 34% of the area of the pipe, reported a sample grade of close to 1 cpht on a total bulk sample of 4 349 dry tonnes of kimberlite from three sample pits, while the Satellite pit reported a sample grade of close to 4.5 cpht based on a bulk sample of 413 dry tonnes of kimberlite.

However, the company stated that while surface grades had been established it was not yet possible to define a mineral resource and, therefore, trail mining was needed. 

"The low-grade nature of the Lemphane kimberlite suggests that it is unlikely to be possible to determine a mineral resource classification beyond the inferred level, because bulk sampling at depth is likely to be unfeasible.

“Therefore, the grade and revenue model for the pipe at depth will be based solely on geological continuity and results from a comprehensive and large-scale trial mining programme at surface,” MSA explained, adding that the principle of establishing a mineral resource estimate from the extrapolation of statistically robust surface production or trial mining results had been successfully applied at Gem Diamond’s Letšeng mine and at Lucara Diamond Corp’s Mothae project.