JOHANNESBURG (miningweekly.com) – Precious metals producer Sibanye-Stillwater on Monday reported that its South African gold reserves had decreased by 10% year-on-year to 25.74-million ounces as at December 31, while its total platinum, palladium, rhodium and gold, or 4E, platinum group metal mineral reserves had declined by 4% year-on-year to 22.36-million ounces.

The decrease in the gold reserves is the result of many factors, including the depletion of 1.4-million ounces mined during 2017. This volume was mitigated by the addition of 1.8-million ounces of gold from exploration of secondary reefs and white areas, primarily at the miner’s Kloof and Driefontein operations.

The local gold reserves were also reduced following the cessation of underground mining at the Cooke 1, 2 and 3 shafts, accounting for 752 000 oz.

Owing to a revised mine plan and increase in pay limit at the Beatrix 4 shaft, 1.6-million ounces was excluded from the overall reserves. This exclusion includes the Beisa project.

A further reduction of 971 000 oz resulted from technical factors, including a change to mine call factor, tail-end management and increased pay limits.

PLATINUM RESERVES
The decrease in 4E PGM reserves was mainly the result of 1.5-million ounces having been mined in 2017.

The reserves were also affected by a revision in the methodology for determining geological losses, by calibrating against actual historical losses, which resulted in a decrease in the overall estimated losses applied to the South Africa PGM operations. This resulted in an increase of two-million ounces in reserves.

In addition, the total reserves volume was impacted by mineral reserves at the Siphumelele mine, which declined by 691 000 oz as a result of the deferral of the Upper Group 2 expansion project. This project will be reviewed subject to an improving economic environment.

An additional 752 000 oz of PGMs were also factored in owing to the removal of subeconomic ounces at the end of the life-of-mine.

However, attributable PGM mineral reserves at Mimosa increased by 20% to two-million ounces, following a successful technical and economic valuation of a part of the South Hill orebody.