DIAMONDS

Rockwell’s big ALLUVIAL MINING IN THE MIDDLE ORANGE

It is a little over two years since alluvial diamond junior Rockwell Diamonds put CEO James Campbell at the helm. Having visited the company’s Middle Orange River operations, one thing is clear – the company has since made a dramatic turnaround, writes Laura Cornish.

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CAMPBELL, HIS OPERATIONAL team and the board members who stand alongside him, are breath-ing life into the company and its

assets, which under previous management was struggling to keep its head above water.

To say the company has made a dramatic turnaround is an understatement. Non-core assets have been sold (Klipdam), new mines and process plants built (to the value of US$3.6 million [R37.01 million]), and fit-for-purpose technologies implemented to deliver best production targets. And the fu-ture for Rockwell Diamonds looks bright as its goal to achieve 500 000 m³/month is well within reach, considering it is more than halfway there (360  000  m³/month) from current production volumes.

“We have also celebrated our fifth consecu-tive quarter of improved dollar denominated revenue, thanks to the increased recovery of large, high-value diamonds,” says Campbell.

Flagship status reinstatedSituated on the south bank of the Orange River, about 50  km south-west of Doug-las, Rockwell Diamonds’ Saxendrift mine is proving it deserves the flagship title once again, having produced substantially more carats in the 2013 financial year (10 276 car-ats) than in 2012 (6 944 carats).

This can be attributed to a number of rea-sons, including Saxendrift Extension (for-merly known as the Jasper project, acquired early this year) and the incorporation of state-of-the-art diamond technology. The newly established Saxendrift Hill Complex (SHC), commissioned in March 2013, should deliver further improvements going  for-wards. “We built the SHC plant for a num-ber of reasons, the primary reason being to incorporate a technology that we believed would improve our recovery capability for larger Type  IIA carats, while reducing op-erational costs when compared to DMS or rotary pans. This concept was also intended as a proof of concept for our large resource Wouterspan asset,” explains Campbell.

Situated on the Saxendrift property, pro-duction ramp-up at the new SHC plant is nearing operational nameplate capacity (100  000  m3 /month) and celebrates what could become a revolutionary change in the local diamond sector. Having successfully pilot-tested a Russian Bourevestnik X-ray bulk sorter for six months to October 2012, which yielded positive results and 1 596 car-ats from old tailings reprocessing, the com-pany purchased an additional sorter, as well as two single particle sorters that now form an integral component of the SHC plant.

Although Rockwell Diamonds was not the first company in South Africa to use the bulk X-ray sorter, it has undoubtedly pioneered the Bourevesnik X-ray in South Africa, being

the first local company to incorporate the technology in both a concentration and recovery mode. Walter Bold, Rockwell Di-amonds’ group engineer, says the first ma-chine imported into the country was used to test tailings material at Lětseng.

“The bulk X-ray plant has a lower environ-mental footprint with lower water consump-tion and power requirements than tradi-tional DMS or pan processing plants. It also picks up flat stones, which no other technol-ogy has successfully achieved,” says Wikus

OPPOSITE Primary crushing circuit at the Niewejaarskraal plant

BELOW James Campbell (left) and Wikus de Winnaar

c meback

“We have also celebrated our fi fth consecutive quarter of improved dollar denominated revenue, thanks to the increased recovery of large, high-value diamonds.” James Campbell, CEO, Rockwell Diamonds

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de Winnaar, Saxendrift mine manager. It also only requires one operator to run the four modules. The capital investment in the project was paid back with gross rev-enue generated from the sale of diamonds recovered during the first two months of production. “It is purely based on diamond detection through luminescence, is me-chanically robust and is an extremely sim-ple process,” adds Bold.

In order to fully evaluate the effective-ness of the bulk X-ray technology, grav-els from the Saxendrift extension project were processed in parallel through both the bulk X-ray system as well as Saxen-drift’s traditional pan plant (with Flow Sort X-ray machines) in July.

Results to date indicate that the X-ray plant is achieving grades at least 40% higher than the conventional plant, and its large stone recovery capability very high (two rough diamonds exceeding 30 carats were recovered in July). The SHC plant is further projected to have 30% lower unit processing costs than the conventional Saxendrift pan plant, providing further commercial benefits.

While the lifespans of Saxendrift and SHC are three and one-and-a-half years respec-tively, the key to operational life beyond that is Saxendrift Extension, which has at least fi ve years of life. “Th is is excluding what we may discover from further explo-ration down the line,” De Winnaar adds.

“Saxendrift Extension is located 5  km uphill from the SHC plant, and this is be-coming a challenge for our Komatsu and Volvo equipment fleet, which is consid-ered old in mining terms. We have brought in a consulting engineer to look at the fleet and help us evaluate various options. This includes doing an extensive midlife overhaul of the kit, to keep it running an-other five years,” Campbell explains.

“The other option is to convert our Dabmar infield screen (which removes all sand, banded iron formation stone and oversize material before going to the main Saxendrift pan plant) to a mobile unit that can be transported into the pit. This would enable us to leave two thirds of the mate-rial in the pit, which would alleviate the pressure on the fleet, enabling it to last the life of mine. Standardising the fleet would also help.”

Campbell says the company opted for a Dabmar screen because it can take mois-ture content of up to 15%. “The Dabmar is the only machine that can dry screen with damp gravels with an efficiency well over 90%.”

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1 BEFORE 105 carat stone from Saxendrift2 AFTER 105 carat Saxendrift stone forms one of pair of exceptional round brilliant cut diamonds3 The fi rst large stones recovered from Niewejaarskraal 4 A sample of the fi rst rough diamonds recovered from the Bulk X-ray pilot project conducted at Saxendrift 5 A 116 carat rough diamond recovered from Saxendrift Extension gravels6 A selection of +10 carat stones recovered from Saxendrift in August 2013

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All but eight of the workforce from Klip-dam accepted a transfer to Niewejaarsk-raal, enabling us not only to preserve jobs, including the opencast contracting staff complement, but also retaining key skills to quickly bring the new mine on stream.”

Production commissioning of the first phase of the new plant started during July 2013, within 10 weeks of the project being approved. The first diamonds recovered included two stones exceeding 20  carats. High diamond values have compensated for slightly lower than anticipated grades for the initial gravels that have been pro-cessed during commissioning, due to a greater variability in the Rooikoppie par-ticle size distribution. The plant efficien-cy was confirmed; however, plant tailings were reprocessed through the bulk X-ray system with no diamonds being recovered.

The plant has been constructed using el-ements of the existing DMS plant that had been on care and maintenance at Niewe-jaarskraal since 2007. The next phase of

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De Winnaar adds: “Ultimately, the suc-cess at Saxendrift, or any alluvial dia-mond project for that matter, requires high volumes to be moved continuously. This makes our fleet an integral part of our business and our production tar-gets. The greater the volumes, the more certainty there is around the number of carats recovered.”

A new star is bornLocated only 8 km (as the crow flies) from Saxendrift, also situated on the south bank of the Middle Orange River, Niewe-jaarskraal has been rejuvenated, taken out of care and maintenance, repaired, upgraded and expanded. And it is already producing diamonds.

The existing DMS plant, originally built by former owner Trans Hex, was recom-missioned and certain plant components incorporated from the sold Klipdam mine. A new DMS plant, a first of its kind in South Africa as well, was installed in September and is currently being tested. Could Rockwell pioneer a new revolu-tionary DMS technology for diamonds? It’s  possible.

“It took about 150 truckloads to trans-port all the necessary components from Klipdam, including the Flow Sort X-ray machines, and a 220 strong workforce came with it. Our investments to grow Middle Orange production will have socio-economic benefits for this region that is impacted by high unemployment.

commissioning entails processing a mix of Palaeo and Rooikoppie gravels, which commenced during the third week of Au-gust when the first blast was carried out to access the main Palaeo deposit that is expected to be the mainstay of operations at Niewejaarskraal. The company has stan-dardised bottom cut-off size of 5  mm for the Middle Orange resources.

Campbell is confident of this project’s performance going forward. “We have contracted CML Operations to do all our mining for us, having previously worked with it to turn Klipdam around before we sold it.”

The combined grade between Rockwell’s mines is approximately 0.5 carats/100 m³. This combines Saxendrift’s average 0.4 with Niewejaarskraal’s 0.6 carats/100 m³. The newest production addition also has a healthy estimated lifespan of 10 years.

“Future growth plans include options to further increase the production capacity at Niewejaarskraal, where we would consider

TOP Dabmar pre-screening plant

ABOVE Mining at Saxendrift extension RIGHT Saxendrift Hill Complex plant where Bourevestnik X-ray sorters are located

The situation at TirisanoThe Tirisano mine, situated just outside of Ventersdorp, has been Rockwell’s problem child since it acquired it in March 2010. After numerous attempts to resolve operational diffi culties, the mine was placed on care and maintenance in December 2012.

During the 2013 fi scal year, Rockwell launched its royalty mining contractor strategy to leverage the value at Tirisano. Smaller areas within the mining right, which are unsuited to a high-volume operating model, are operated by smaller operators who can mine these sections economically. The royalty miners incur all operational costs for these activities while Rockwell maintains responsibility for diamond security and generates a 12.5% royalty on diamond sales.

At the end of this year, there will be fi ve different contractors on-site, after which monthly volumes are expected to exceed 150 000 m³/month.

Rockwell Diamonds has undoubtedly pioneered the Bourevesnik X-ray in South Africa

Please contact jm@dabmar.co.za

or c +27 (0)82 449 5919

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the BV technology. We are also evaluat-ing the next steps at Wouterspan, both of which would have flow through benefits for employment in the region.”

An even brighter futureDr Kurt Petersen, a doctor of diamond metallurgy, has completed a preliminary economic assessment on Rockwell’s Wou-terspan property, situated between Saxen-drift and Niewejaarskraal.

The study indicated positive economics, sufficient to take the project to the de-tailed design stage.

Key assumptions of the study include a 1  200  tph or 354  000 m³/month plant comprising three processing streams, two Bourevestnik bulk X-ray systems to handle the course and mid-sized gravels and the third stream being a DMS to process fine material. This would make it by far the largest operation in the Rockwell stable.

“We have a preference for contract mining and will use this model for Wou-terspan. Because it is large, we will look at developing it in a phased approach

using equipment we already have on-site, hopefully starting early next year,” Campbell indicates.

Rockwell Diamonds has made a big ‘come-back’ in the Middle Orange River region and is set to grow even bigger over the next few years. With the right management in

place, it appears this company is capable of anything when it comes to successfully mining alluvial diamonds, especially with great technology driving the process.

Screened material, which will be transported to SHC

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