Shaun Graham, Mining and Geoscience Applications Developer at Carl Zeiss Microscopy, talks to Ellis Davies about the mining applications of the Versa X-ray microscope.
Tell me about your role at Zeiss.
I joined Zeiss in 2014 as an applications specialist. Over the past 18 months I have been involved in product development for solutions that serve mining and geoscience applications, with access to the light, electron and X-ray microscopes and automated mineralogy software that Zeiss develops. It is up to my colleagues and I to develop applications and strategically place products in the marketplace.
What is the Versa X-ray microscope?
The X-ray microscopes were a piece of technology that Zeiss obtained three-or-four years ago when it acquired Xradia, USA, which was famous for building synchrotrons. This move was made because of the company’s unique technology, and we gained a range of X-ray microscopes and computer tomography capabilities for our portfolio.
A lot of the technology that sits in the Versa has been developed in the synchrotron community, so the main applications involve looking at things in 3D at very high resolution. Because of the architecture of the Versa, which allows us to look at large samples at high resolution (known as resolution at a distance), we sought to find applications in the mining industry. Some of these are being explored currently, and some are quite exciting and either solve problems with conventional 2D analyses or build on the 2D data sets.
How is the Versa an improvement on 2D analysis?
2D analysis has been widely used in industry for many years, and the limitations of the method have been accepted and certain things have been put in place to get around them, such as taking lots of samples and trying to increase your statistics that way. For a 2D section, there will be bias or error from sample size and quantity, as well as from looking at a 2D plain through a complex 3D object. This can implement a stereological bias into the analysis. Because we’re dealing with volumes in the computed tomography (CT) system of the X-ray microscope, we can circumvent some of these, in particular when looking at trace metals or metals with high tenors, such as platinum and gold, which are often found in low concentrations. If we were trying to find metal with such low concentrations in a 2D analysis, we would need to look at lots of samples to get the right statistics. With the CT system it is possible to quickly create one sample and analyse it with superior results and understanding of where those grains of precious metal are located.
What are the key features of the Versa?
The main feature is the internal architecture, which is composed of a dual magnification process. During this, X-rays pass through the sample and interact with the scintillator, which is connected to a calibrated objective, and are converted to light. This gives us a greater ability to focus the light, and we can deal with larger samples while maintaining a higher resolution.
We have developed a workflow where we are able to scan large volumes and change the objectives, then zoom in to the region of interest at a much higher resolution – this is known as ‘scout and zoom’. The great thing here is that it does not require any additional sample preparation.
How would the Versa be used in mining?
At the moment we are on the cusp of a paradigm shift where people are starting to look at the technology and see applications. The mining industry is just coming out of a four-to-five year cycle of low metal prices and employment, and people are starting to use this system to look at the front end of the analysis when looking at drill core and trying to understand the geometallurgy block models. There are also applications in feed forward type analysis, where after drilling or blasting we can quickly scan a large volume of the blast particles to get a very quick understanding of the model mineralogy and texture, which can help send the material to the right stream into the processing plant.
Looking at applications specific to floatation and leaching, we are looking at using the 3D rendered data sets to understand things like liberation and particle exposure, and find a way to recover those metals. If we take that concept and pass it to a more research heavy field, we can house the sample in an in-situ flow cell, which allows us to pass fluids through it and image them, providing insight into the fundamental processes during leaching. This is a new capability that has never been possible and allows us to understand the relationship of texture, liberation and the fluid-particle interaction in our heap leach systems. We can also use this analysis and data to understand tailings and try to minimise losses. Where gangue material is thrown away there might be some gold left, and the CT system is a great way of scouting through those samples to understand the mineralogy and textural association of those losses. That can be passed back into the processing plant to better understand how to optimise the processes of recovery.
One final application, and one I’ve been working on closely, is acid-mine drainage, which is making sure that the gangue and waste material at the end of a mine’s life is not reactive in its environment and that acid rock drainage is controlled and minimised.
Is it time and cost effective?
Definitely. 2D analysis, for example, is very time consuming in both the analysis and the preparation of the samples. A CT sample preparation only takes a few minutes, compared with hours or days for a 2D analysis. In terms of cost, if you’re a gold company and you can start recovering that one-gram per tonne that you’ve previously thrown away at the end of each day, it doesn’t take very long to get a return on investment from acting on the data this instrument can provide. Interestingly enough, in the industry people widely apply 2D analysis and get substantial buybacks and optimisations, and the CT systems is just another way to add a further level of data and allow greater value generation and processing optimisation.
What are the future plans for this product?
In terms of its application in the mining industry, we have only just begun to understand the advantages and cost benefits that can be delivered. The technology and the internal architecture are unique to the Zeiss system, and we will continue to develop and push that further. The real value is the software, which is able to extract the data. We will continue to develop and apply this software to provide a comprehensive solution.
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