Tag Archives: XRF

De Beers diamond XRF technology optimises sorting at emerald mine

De Beers Group Technology has adapted one of its X-ray fluorescence (XRF) diamond sorting range of machines to create “a secure and efficient sorting solution for emeralds”, it says.

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.

“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,” Taylor said.

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

In its trial mining and processing phase, Gravelotte has been gathering data to confirm the historic grades previously recovered at the project. In operation for much of the 20th century, total recorded production from this area was estimated at nearly 113 Mct. It was reportedly the world’s largest emerald mine of its type in the 1960s, employing over 400 sorters, De Beers said.

General Manager of Operations at Gravelotte, Wessel Marais, said the traditional manual method of sorting carried an associated security risk and led to less than optimal recoveries.

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

He says testing of samples provided by Magnum came out with successful results.

“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 noted 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 said.

The De Beers Group Technology emerald sorting machine can make a potentially significant contribution to the success of the Gravelotte operation, according to De Beers, with its high recoveries combined with excellent processing security. The project aims to reach a target of around 3 Mct/y 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 concluded.

XRF ore sorting shows potential at Yukon zinc project

X-ray fluorescence (XRF) ore sorting technology has found another fan after Fireweed Zinc reported positive results from preconcentration test work at its Macmillan Pass zinc project in the Yukon of Canada.

Samples from Macmillan Pass’ Boundary Zone, a discrete bulk-tonnage, exploration target 15 km northwest of the Jason zinc-lead-silver deposit, were put through XRF, X-ray transmission, electromagnetic and dense media separation sorting tests by Canada’s Sacré-Davey Engineering at the University of British Columbia, with XRF showing the most promising results, Fireweed said.

The principal results of the 436 rock samples tested in the XRF trials included the potential to upgrade the feed grade from 2.5% Zn to 5% Zn and a rejection rate of 70-50%, with zinc recoveries ranging from 80-85%.

Fireweed pointed out that the analysis in the study assumed that 25% of the feed had fines (-12 mm) which cannot be processed in the ore sorter. As a result of this, the fines would bypass the sorter and combine with the ore sorter product, with the final grade of 5% Zn achieved after combining the ore sorter product with the fines assumed to have a grade of 2.5% Zn.

XRF sorting is currently used at over 50 operations across the world, including Hecla Mining’s San Sebastian mine, in Mexico, and Anglo American’s Mogalakwena mine, in South Africa, according to Fireweed.

Typically, it uses an XRF sensor to distinguish and measure surface metal abundances on rock pieces moving on an enclosed conveyor belt unit. The XRF readings for each individual rock are then analysed by high speed software to distinguish and flag rocks with metal values above and below a set threshold.

At the end of the conveyor belt, focused high pressure air jets or mechanical levers then separate the designated higher-grade rock pieces for processing and reject low grade and waste pieces. The amenability to ore sorting depends on the material characteristics of a deposit.

Fireweed said: “The Boundary Zone samples responded positively to XRF testing because zinc values on the surfaces of individual rock pieces correlate closely with the overall zinc assays of those rocks.”

Fireweed Zinc CEO, Brandon Macdonald, said the ore sorting results imply there is potential to improve the economics of the Macmillan Pass project.

He continued: “These results suggest that we may be able to reject 50% to 70% of low-grade and waste rock at low cost near a potential open-pit operation at Boundary with less than 15% loss of zinc mineralisation before material is transported to a central processing plant at Tom.”

Macdonald said the company has now moved the drill to Boundary to both confirm and step out from historic holes, as well as obtain a 2 t sample to confirm these ore sorting results may be obtained on a larger scale.

“If the larger test is successful, we can then incorporate the benefits of an XRF ore sorting system at Boundary into a revised preliminary economic assessment economic study along with upgraded information from recent drilling at Tom, Jason and End Zones.”

A 2018 preliminary economic assessment at Macmillan Pass showed that a 4,900 t/d operation could be constructed for an initial capital C$404 million ($305.9 million) using starter-pits on the Tom West and Jason Main zones.

This plan would result in average yearly contained-metal production of 85,000 t of zinc, 48,000 t of lead and 2 Moz of silver over an 18-year life, with an after-tax net present value (8% discount) of C$448 million generated.

CSIRO and Gekko’s OLGA receiving good reception at Queensland gold mine

Field trials for the CSIRO-developed Online Gold Analyser (OLGA) are showing such positive results at a Queensland gold mine that the technology is expected to be ready for market this year, the research organisation reported recently.

OLGA is an X-ray fluorescence-based technology capable of detecting gold in slurry with around 1,000-times better accuracy than conventional methods – and in real time, according to CSIRO.#

The analyser, which will be available through technology and services company Gekko Systems, detects gold (and other elements) contained in a continuous process stream.

OLGA can detect gold in slurries at 10 parts per billion using a pair of X-ray lenses that greatly magnify the slurry’s fluorescent gold signal as it passes through a tank.

“Normally you take samples from a stream and send that sample to a laboratory,” CSIRO Research Group Leader, Yves Van Haarlem, said. “If you’re lucky the lab is onsite, but even then the turnaround time for analysis can be 10 to 12 hours. That’s probably too late to do something about it. With OLGA you can act on what you’re seeing almost immediately.”

Conventional X-ray Fluorescence is already a well-known tool in the base metals industry for the monitoring and control of concentration plants, but they tend to have less accurate detection limits – usually in the tens to hundreds of parts-per-million (ppm) range, precluding their use in precious metal concentrators, according to CSIRO.

Richard Goldberg, Gekko’s Head of Innovation and Collaboration, said that other means of detecting gold have been lacking in accuracy and/or the timely availability of results. “We’ve never had the ability to directly monitor gold flows through a plant in real time before,” Dr Goldberg said. “We know that gold grade can vary over relatively short periods and that it will do so between the samples taken as part of traditional process control regimes. As the results from those samples are also delayed, they are unlikely to accurately reflect the changes occurring in the process stream.”

Dr Goldberg said OLGA’s value stems from its ability to provide important information in near real time. In effect, the operators of a plant will no longer be blind to changes in its performance, according to CSIRO.

Andrew Dixon, Gekko’s Performance Consultant Manager, said the new system is proving its triple bottom line credentials. Economically OLGA allows the processing plant to be controlled to allow maximum efficiency of gold recovery, he said.

“This has environmental benefits as well. It will allow you to optimise reagent additions and to reduce any emissions from the plant that may have to be detoxified or treated to be made safe,” he said.

This means a plant will end up with less reagent chemicals in the tailings.

“It’s also more sustainable – the efficiency improvements will have an effect on the stability of the operation,” Dixon said. “A more stable gold processing operation is always going to be more efficient.”

Dr Goldberg said the reaction from gold mining companies that have seen OLGA work in laboratory conditions has been extremely positive and have seen considerable interest in the technology.

“We’re currently conducting field trials to ensure it’s a solid product before we fully release it to the market. To date, the trials have been extremely positive,” he said.

Dr Van Haarlem said Gekko has been the ideal partner for CSIRO on this technology. “Gekko engineered the whole structure around the analyser so that the slurry can be easily analysed, validation samples can easily be taken, and to provide the robustness required for plant installation,” he said.

OLGA is not just about detecting gold concentration. It’s about providing information, according to CSIRO.

“You could, for instance, put OLGA on the feed stream and one on the tailings,” Dr Van Haarlem said. “You could then look at what went in and what went out. If there’s too much gold in the tailings compared to the feed then the plant knows immediately that it’s losing gold. All this can then be acted upon.”

Dr Goldberg said there has been interest from potential buyers from as far away as Africa, Europe and South America. A fully supported product should be available for these regions later this year, CSIRO said.

Dr Van Haarlem said the X-ray optic system is now being tested on platinum and can be used for other metals. Its application could be much more widespread, such as for detecting toxic elements in food and water.

Yet, he believes OLGA’s future rests in its potential to revolutionise gold processing plant strategies and to refine logistics.

“It will provide a lot of data on real time gold and slurry density, which can then be correlated with other plant parameters,” he said. “It might turn out that if you don’t mill the ore sufficiently, gold recovery suffers. It’s going to show us correlations we didn’t even know were happening. This information can help us to optimise the entire production circuit.”

MineSense front and centre in bulk ore sorting game

Having just commercialised its bulk ore sorting technology at Teck Resources’ Highland Valley Copper (HVC) operations in British Columbia, Canada, MineSense is looking to show the wider industry just how effective this pre-concentration process can be.

IM spoke with President and CEO, Jeff More, to find out more about the company’s ShovelSense and BeltSense technologies and how the Vancouver-based startup has been able to secure investment from the likes of ABB, Caterpillar and Mitsubishi.

IM: Can you explain in a little more detail how your ShovelSense and BeltSense solutions work?

JM: The base technology for both is X-ray Fluorescence (XRF) – a technology that has been around for some time. What we have done to this existing technology, which is quite unique, is three things:

  • One, we have extended dramatically the range of XRF. Traditionally XRF would almost have to be held to the surface of a rock to get accurate measurements. The range extension allows us to work in the shovel environment where we are working across metres of volume;
  • Second is speed. Our system is extremely fast. High speed analysis is required on our conveyor belt applications, but this is even more important in the shovel, where we’re measuring dynamically; as the material is flowing into the shovel, to get a representative reading, you have to be able to take very fast readings of the material as it is moving past the sensors;
  • The third is robustness. On a shovel, you are in a nasty environment from a shock and vibration perspective. We developed a system with sensitive components – the XRF itself, as well as the computing devices around it – that can stand up to that very high shock- and vibration-type environment.

IM: The most high-profile examples of the application of your ShovelSense technology have been at copper mines (HVC, in particular); is the detection technology particularly effective in these ores? Is it being trialled elsewhere?

JM: The current sensing we have with the XRF is very effective in a certain section of the periodic table, which nicely covers the major base metals. We’re focused on copper, nickel, zinc and polymetallic versions of those three. The fourth area of focus is iron ore.

We’ve selected copper as our first focus because of the size of the market and the geography. We have done most of our work in copper, but we now also have operating systems in nickel and zinc.

On a lab scale, the technology has been very effective in iron ore, but iron ore is a very different flow sheet, so we have purposely set it as our fourth market in what we call our primary clusters.

We have five mine site customers at the moment – three copper, one zinc-lead and one nickel-polymetallic.

We were very much focused on North America and, in particular, British Columbia for our first pilots and trials as it was quite easy for us to service in our back yard. The first international market was Chile, for obvious reasons in terms of copper production, and we now have a full MineSense entity and team operating in Chile and Peru.

We’re staggering the rest of our global expansion. We’re now quite active from a business development perspective in southern Africa – South Africa, Zambia, DRC – and have activity in Australia.

We have Systems installed at two different copper mines in British Columbia, one at a very large nickel-polymetallic complex in Sudbury, Ontario, and will have a fourth system operating in Alaska. We also have two mines, but four systems, operating in Chile. By the end of Q2, we will have another three systems operating in Chile.

We did all our development work for the system at Teck’s HVC operation and we’re now completely commercial there. We officially commissioned our first system in December, the second system is being commissioned as we speak and the third and fourth will be installed and commissioned in late-March. This will completely equip their fleet.

IM: Teck has previously said the use of ShovelSense has resulted in “a net measurable increase in the amount of ore (and the associated head grade)” it has available to feed its mill at HVC. Are these results in keeping with your expectations for the technology?

JM: Yes, absolutely. We base everything on, what we call, our value model. Very early in our engagement process, we set out a detailed model that calculates the profit improvement that mine will see – we did the same for Teck HVC.

We agreed on a target at HVC and are actually exceeding that estimate. Most importantly, Teck is also seeing that value and is estimating a great overall impact at that mine.

This is an abridged version of a Q&A to be published in the ore sorting feature in the March issue of International Mining.

Hecla testing out XRF ore sorting at San Sebastian silver-gold mine in Mexico

Hecla Mining is carrying out ore sorting proof of concept work at its San Sebastian silver-gold mine in Durango, Mexico, CEO Phil Baker told attendees at the Mines and Technology conference this week.

Baker said an algorithm based on X-ray Fluorescence (XRF) technology was determining whether the rock coming through from the mine was ore or waste.

San Sebastian, which produced 3.3 Moz of silver and 25,177 oz of gold last year, recently moved over to underground operations after open-pit mining concluded at the end of 2017. In 2018, it is expected to produce 2-2.2 Moz of silver at a cash cost, after by-product credits, of $9.50/oz, while gold production is expected to come in at 15,000-16,000 oz.

The company’s concession holdings in Durango are in the middle of the prolific Mexican Silver Belt and cover approximately 42,000 ha. Mineralisation in the district is structurally controlled and hosted in sedimentary rocks, with many companies in the region mining high-grade veins.

Hecla is weighing up whether to start mining sulphide ore at the deposit, which could potentially extend the mine’s life by some five years.

While Baker said test work on XRF ore sorting at San Sebastian was ongoing, he did see potential for the technology being applied across the mining sector.

“The real issue with ore sorting is: what is your recovery going to be? How much are you going to lose? And, we’re still working through that (at San Sebastian). But I have high hopes for this being a complete gamechanger for the industry,” he said at the event in London.

“The cost of sorting is quite low. If you’re able to get a high enough recovery, then you can afford to do more productive methods of mining for small tonnage operations. It could completely change how you go about mining.”

Last month, Agnico Eagle Mines said it was in the process of installing an ore sorting pilot plant at its Pinos Altos gold-silver operation, also in Mexico.