JSE-listed Gemfields is “particularly encouraged” by the increased level of mineral resource base and confidence underpinning the company’s most recent competent persons reports (CPR), despite results showing a decline since 2015.
The CPR, which was produced by SRK Consulting in respect of Montepuez Ruby Mining (MRM), which is 75%-owned by Gemfields, includes mineral resource and mineral reserve estimates in accordance with the 2016 edition of the South African Code for the Reporting of Exploration Results, Mineral Resources and Mineral Reserves (Samrec).
The CPR highlights a total of 60.2-million tonnes of secondary mineral resource and 1.4-million tonnes of primary mineral resource at an average of 6.2 ct/t and 97.9 ct/t of ruby content, respectively.
Of the total mineral resource of 61.6-million tonnes, 21.6-million tonnes have been classified in the indicated category. The remaining 40-million tonnes have been classified in the inferred category, pending further validation of the mineralisation grade by way of bulk sampling.
Gemfields also said in a news release on Monday that the post-tax net present value (NPV) is estimated at $527-million at a discount rate of 10%, with a planned life-of-mine (LoM) of 15 years, based on the 21.6-million tonnes of probable mineral reserves.
In comparison with the previous report, a maiden Joint Ore Reserves Committee- (Jorc-) compliant resource statement was prepared in respect of MRM in 2015.
Since then, further auger drilling has been carried out across the licence area, extending the explored area from 36 km2 to 77 km2.
This, Gemfields said, presented an opportunity to conduct paleo-drainage analysis alongside other geological investigations.
“When combined with the experience gained from actual mining and ongoing bulk-sampling operations, the result is a much better understanding of the mineralisation characteristics in the secondary deposit environment across a wider geographical area, as well as improved insight into ore grade variations in the eight spatial domains now identified and which cover 77 km2,” the miner explained on Monday.
While these eight domains are considered to be of similar grade and geological control, only four of the domains host noteworthy bulk sampling pits. These, Gemfields said, are the only domains included in the indicated mineral resource, in keeping with Samrec.
As such, data from the four domains with bulk sampling exercises has not been extrapolated to the remaining four domains.
According to the news release, the improved level of evidence-based confidence in the mineral resource, combined with a switch from the Jorc-compliant resource statement to Samrec-based reporting, mean that the LoM and associated NPV have been adversely impacted when compared with the 2015 Jorc CPR, referring to 21 years and $996-million, respectively.
Future bulk sampling in the remaining four domains will provide grade estimates in these areas and, therefore, present an opportunity to augment the LoM and associated NPV, Gemfields added.
Gemfields MD for Mozambique and Ethiopia Kartikeya Parikshya said that while the headline LoM and NPV figures have ostensiblty declined, in reality, the company’s understanding of, and confidence in, the MRM deposits have improved materially.
“We are particularly encouraged by the increased level of mineral resource base and confidence underpinning the latest CPR.”