Mining at Montepuez is an open-pit operation, which means no tunnels, and a largely mechanised process to scoop up the gravel and gemstones for sorting.
Montepuez Ruby Mine
About MRM
The existence of rubies in Montepuez, in northeast Mozambique, became widely known in 2009.
Today, the Montepuez ruby mine in Cabo Delgado province covers 33,600 hectares of one of the most significant ruby deposits in the world. Gemfields owns 75% of Montepuez Ruby Mining Limitada (“MRM”). The remaining 25% is owned by Mwiriti Limitada, a local Mozambican company.
Since operations began in 2012, Gemfields has established world-leading facilities and transformed the communities that surround it. MRM provides employment (both direct and via contractors) to 1,400 people, 95% of whom are Mozambican nationals.
Ruby Mining at Montepuez
Mozambican rubies can be found in gravel – from close to the surface to some six metres below.
There are two sources of rubies here – the original rock formation, which has been undisturbed since its formation some 500 million years ago, and secondary deposits, where the gemstones were stirred by ancient rivers, now long gone, tumbling gems downstream.
These secondary deposits often hold the higher value rubies, as any brittle, lower-quality material was swept away in turbulent waters.
To reach the gemstones, the topsoil is first removed. It is saved to be returned with planted indigenous flora once mining is complete.
The recovered gravel, known as ore, is processed at the wash plant using recycled water, Here a dense medium separation plant, or DMS, sorts the pieces by weight. This pioneering process is highly effective, even at speed, allowing considerable ore to be processed efficiently.
From here, rubies enter our industry-leading sort house, which are equipped with state-of-the-art optical sorting machines, These machines use ultraviolet light to identify individual gemstones and jets of air to push them free.
The remaining gravel is sorted by hand in sealed, windowed boxes before being graded for colour, size, shape and clarity.
The carefully graded rubies then head off to auction, with the proceeds fully repatriated to Mozambique and all royalties due to the government paid on the full sales price.
After auction, the gemstones enter the international markets to be traded as rough, or cut and polished by skilled hands, usually in Thailand, before being sold to jewellery houses, designers, collectors or gemstone traders.
How Rubies are Formed
Northeastern Mozambique is at a unique, geologically critical junction between two treasure-bearing belts of rock, formed between 500 and 800 million years ago.
The highlands of northern Mozambique are dominated by a Precambrian basement section of the well-known Mozambique Belt that extends up north to the Mediterranean. In its basement, large regions were metamorphosed at a high temperature and high pressure during the Pan-African tectonic event, creating suitable conditions for the formation of gemstones. Deposits of the Pan-African Orogeny are much older than the Himalayan range gem deposits (e.g. Myanmar rubies) that are only 40-million-years old.
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