Cobra North Pit blast material being loaded

Phase 2 of the trial mining programme has just begun at Magnum Mining and Exploration’s Gravelotte emerald project in South Africa as a means to evaluate and determine the best mining processing and sorting techniques.

South Africa – In 2018 Magnum Mining and Exploration completed the first stage of this evaluation programme by the trial processing of around 500 t of rock from the existing waste and low grade dumps at Gravelotte. This first stage programme provided valuable information on the crushing characteristics of Gravelotte rocks and determined that XRF technology was the most efficient and accurate sorting method to liberate the emeralds.

The second and final stage of the evaluation programme is the trial mining, processing and sorting of around 8 000 t of rock from the historic Cobra North and Discovery pits at Gravelotte.

The mining stage of this programme has now commenced and is anticipated to take around 20 to 25 days to complete. Mining is through drill and blast and excavation into short haul trucks to the stockpile area adjacent to the processing circuit.

The processing circuit has been constructed locally to Magnum Mining and Exploration’s design and specifications and will commence processing the mined material in late March after a short commissioning period using material from the low grade and waste dumps.

The first stage trial processing programme indicated that XRF is a more efficient and accurate sorting method to that of optical or hand sorting. As a result, an XRF unit is scheduled to be commissioned on site during the first week of April 2019.

Based on the historic average mining grade of 6 g/t (30 carats per tonne) this second stage trial mining programme is targeted to achieve in excess of 250 000 carat of emeralds.

The trial processing and mining operations at Gravelotte have been greatly assisted by all necessary infrastructure being already established on site. This infrastructure includes mess, accommodation and mine administration buildings, water and power and large work sheds for plant and equipment.

Gravelotte project at a glance

Magnum Mining and Exploration’s 74%-owned Gravelotte project is located in the Limpopo province of South Africa. Emeralds were discovered in the 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 emerald mine of its type in the world, employing over 400 sorters.

The Gravelotte project provides Magnum Mining and Exploration with a medium term production opportunity in a niche commodity such as emeralds where demand is growing.

The project offers established infrastructure, existing and accessible open cuts together with extensive low grade dumps, a large (albeit incomplete) historic data base, a nearby and available work force, local on-site technical expertise and a nearby township that can serve as a supply centre.

During the past three years, the company 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 company has maintained and refurbished much of the extensive mine site infrastructure at Gravelotte including offices, laboratory, workshops, garages, management accommodation complex and a mine hostel to accommodate mine workers. The mine site is well situated with utilities and logistics being serviced by Eskom grid power, has a sealed road to the mine gate and has a working airstrip.

To read more about Phase 1 of trial mining click here