emeralds
De Beers Group Technology diamond X-ray sorter

By adapting one of its X-ray fluorescence (XRF) diamond sorting range of machines, De Beers Group Technology has created a secure and efficient sorting solution for emeralds.

According to De Beers Group Technology head Gordon Taylor, the company’s sorting technologies have been applied to a range of minerals apart from diamonds, and these include gemstones like rubies to lower value commodities like manganese and coal.

This article first appeared in Mining Review Africa Issue 11, 2019
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“We are always on the look-out for new applications for our sorting equipment, which also employ X-ray luminescence, X-ray transmission, laser, magnetics and ultra-violet technologies,” says Taylor.

“So we were excited by the opportunity to collaborate with Magnum Mining and Exploration on their Gravelotte emerald project in Limpopo province.”

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In its trial mining and processing phase, Gravelotte has been gathering data to confirm the historic grades previously recovered at the Gravelotte project. In operation for much of the 20th century, total recorded production from this area was estimated at nearly 113 million carats.

It was reportedly the world’s largest emerald mine of its type in the 1960s, employing over 400 sorters.

General manager of operations at Gravelotte, Wessel Marais, highlights that the traditional manual method of sorting carried an associated security risk and also led to recoveries that were not optimum.

“Various mechanical sorting options are available on the market today,” says Marais, “and Magnum approached De Beers Group Technology to determine whether their diamond sorting technology could be adapted to emerald sorting.”

He says that testing of samples provided by Magnum was highly successful.

“This led to Magnum leasing an XRF machine from De Beers Group Technology for the duration of our trial mining, and the results to date have been very encouraging,” he says.

“With the machines now deployed in the operational environment, research and development work is continuing in conjunction with De Beers Group Technology to refine the process.”

Taylor notes that constructive collaboration with customers is often an important element in extending the application of De Beers Group Technology’s equipment.

“On this project, we were able to conduct some fundamental investigation on the properties of emeralds to guide us in developing the most effective solution,” he says.

Nico van Zyl, De Beers Group Technology marketing and new business development manager, agrees.

“You really need a partner who is willing to cooperate with you, as there is considerable effort that each has to contribute,” says van Zyl.

“Our team is always enthusiastic about exploring new applications, and has the expertise and experience to know what is possible and how to achieve it.”

The De Beers Group Technology emerald sorting machine can make a potentially significant contribution to the success of the Gravelotte operation, with its high recoveries combined with excellent processing security.

The project aims to reach a target of around 3 million carats a year as its initial production rate.

Before the run-of-mine material reaches the De Beers Group Technology XRF machine, it is crushed to -30 mm and put through a trommel screen for cleaning and further size reduction.

After material containing emeralds is ejected from the material stream by the sorter, it is further sorted by hand and graded.

“De Beers Group Technology is constantly pushing the boundaries where our equipment can be applied, and has had significant successes in non-diamond commodities.

“Whether removing the value product or the waste from the process stream, our sorting technologies can be the game-changer in the viability of many projects,” Taylor concludes.