Trial mining at ASX-listed’s 74%-owned Gravelotte emerald project in the Limpopo province of South Africa is well underway with the start of the processing programme expected to begin imminently.
Phase 1 of the 2-phase 10 000 t trial mining and processing programme at Gravelotte began in Late February with the mobilisation of contractors to site. Mining of around 2 100 t from waste dumps has now has been completed and processing of this material – which will involve crushing, screening and hand sorting has just started.
The second phase will mine and process 8 000 t of hard rock sourced from the Cobra and Discovery pits and will commence in April 2018. The hard rock mining and crushing activities are planned to be completed within the June quarter.
The overall objective of the trial mining programme is to provide critical information to assist with the re-establishment of commercial mining operations at Gravelotte – which was a major producer of emeralds over several decades up until the early 1980s.
The programme is designed to confirm historical emerald grades, optimise mining and processing techniques and recoveries, and allow the company to establish the value of the emeralds produced in the open market.
Magnum Mining & Exploration is targeting recovery of +250 000 carats of emeralds from the total trial mining and processing programme.
Emeralds were discovered in the Limpopo Province in 1927 and, since then, several companies have explored for and mined within the broader region for emeralds.
From 1929 to 1982, the total recorded emerald production from the Gravelotte project – as well as the area surrounding the nearby Gravelotte township – was nearly 113 million carats.
It is reported that, during the 1960’s, the Gravelotte Project itself was the largest mine of its type in the world, employing over 400 sorters.
An extensive database of information is available for the Gravelotte Project. This database covers the historical open pits – Cobra North, Cobra South and Discovery.
The Cobra pits were developed on a hill and only mined to approximately 10 m below plain level, while the Discovery pit was developed near the cessation of historic mine operations and at its deepest point is only around 25 m below plain level.
Historical records indicate that the average recovered grade from hard rock mining in the final two decades of mining was around 6.2 g/t (31 carats/t).
Included within the mining lease are an estimated 850 000 t of coarse tailings and untreated ore, contained within multiple dumps. The dumps are mostly from the historic mining and processing of the Cobra and Discovery pits.
Mine records show that, in the period from 1977 to 1982, an estimated 50 000 t from the dumps were processed for a recovered grade of 2.7g/t of emerald (13.5 carats/t).
During the past 36 months, Magnum has worked to re-establish the historical database and develop a strong understanding of the geology, structure and controls of mineralisation within the project area. The trial mining and programme will allow Magnum Mining & Exploration to enhance its knowledge of the various parameters to re-establish an emerald mining and processing operation in South Africa.
The company has maintained extensive mine site infrastructure at Gravelotte including:
- Mine offices, laboratory, administration offices and health clinic;
- Seventeen on-site three bedroom houses;
- Management accommodation complex, club house, swimming pool and social amenities;
- Workshop and garages; and
- Mine hostel that can accommodate 350 mine workers.
In addition, the mine site is serviced by an Eskom grid power, has a sealed road to the mine gate and has a working airstrip and explosives magazine.