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31 July 2017 4 min read

Article from resourceful: Issue 12


3D sample structure linked with 2D x-ray fluorescence map of sample chemistry of a graphite resource.

The word graphite derives from the Greek word 'grephein', which means to write or draw. Graphite's uses extend beyond creative paints and pencils to batteries, crucibles, refractory bricks, car brakes and for printing electrotypes.

It's a metamorphic mineral, with approximately one million tonnes sold annually in the form of tiny graphite flakes ranging from 1-300 microns, mostly sourced from China and Brazil.

"A lot of work is going into diversifying the sources of graphite, as it's expected to be in increasingly high demand for lithium-ion batteries," Dr Mark Pearce, CSIRO research scientist, says.

"Many graphite deposits around the world are in ancient rocks whose geology is poorly understood.

These rocks have been metamorphosed – heated and put under pressure – numerous times with the potential for fluids to move minerals, including graphite, around to produce rich zones."

Dr Pearce says the crystallinity of graphite grows with increasing temperature, as the organic matter (dead bacteria or plants in younger rocks) is "cooked up" and converted to graphite.

"The geological history of the rocks is important in determining the quality of the graphite present, since the market price for graphite is determined in part by the flake size," Dr Pearce says.

"Our characterisation work helps to determine the history of these rocks. It also allows us to look at the variability in the minerals that accompany the graphite so that it can be taken into account for processing."

Characterising Kibaran Resources' Epanko Deposit

Kibaran Resources is an ASX-listed exploration company focused on unlocking the graphite potential of the mineral-rich landscapes of Tanzania in east Africa.

The company's primary focus is on their Epanko Deposit – a key graphite target that has been identified to host large flake graphite.

"CSIRO studied the metamorphic gradient and process of the Epanko deposit," Andrew Spinks, Kibaran Resources managing director, says.

"This study supported the recently completed bankable feasibility study, which shows that Epanko holds world-class graphite.

"The results have been incorporated into the downstream processing of Epanko graphite for the production of battery grade graphite. Understanding why Epanko has such high grade, combined with large flake, has been critical to position the resource for the enormous graphite growth forecast."

This research and similar work will increase the geological knowledge around Kibaran's several graphite prospects throughout Tanzania, making them more feasible as mines.

Working with Talga Resources on characterisation
Characterisation image shows the make-up of the graphite ore.

Another company seeking to become a global leader in bulk graphene and graphite supply, Talga Resources, owns five graphite projects in northern Sweden which cover the full range of market flake size specifications.

This includes the largest deposits defined in Europe and the highest grade graphite mineral resource in the world. The company has its own unique low cost process to liberate graphite, as well as bulk quantities of graphene.

"Talga's graphite has a long geological history of approximately 1.8 billion years and what we are doing is exploring the properties of this ore to make the world's lowest cost bulk graphene," Mark Thompson, Talga Resources managing director, says.

"We worked with CSIRO to obtain a greater understanding of our most unique graphite deposit via mineralogical characterisation at a larger scale than provided by our nanotechnology research programs."

Dr Pearce adds that Talga Resources own a large graphite deposit in northern Sweden that contains so much graphite that the rocks actually conduct enough electricity to complete a circuit with a battery and a light bulb.

"Talga was developing a novel processing method using electrolysis and wanted to understand what minerals the rocks contained that could impede or improve it. They were also interested in how the graphite flakes were aligned to enable the extreme conductivity and new processing method to work," Dr Pearce says.

Comprehensive analysis of the Nunasvaara graphite deposit

CSIRO analysed the microstructures of four ore samples from the Nunasvaara graphite deposit using a variety of techniques to quantify variations in chemistry, mineralogy and graphite grain size.

Core-scale chemical maps were made using an x-ray fluorescence mapper and areas of interest were selected for more in-depth analysis, based on their microstructures.

"The final stage of the project was to do detailed analysis of the graphite and the other minerals present using scanning electron microscopes to image the rocks at the micro-scale," Dr Pearce says.

"We produced maps of the graphite flakes and other minerals that Talga could then use to understand how the ore was so conductive and how the graphite may break up during processing.

"We also deduced the geological history of these ancient rocks and measurements of carbon isotope ratios showed that the graphite was in the rocks when they were initially laid down as sediments."

Mr Thompson says it was vitally important to be able exfoliate the rock into individual one-atom-thick sheets of graphene, which fetches much higher prices than graphite.

Graphene’s advantages are that it is 300 times stronger than steel, its electrical current density is at least 10 times higher than copper and due to its use in super batteries, conductive concrete, flexible semiconductors and water filtration, it has the potential to be a key player in the development and change of multiple industries.

"It's very expensive and hard to make graphene," Mr Thompson says.

"Working with CSIRO helped us to optimise exploration for the right style of deposit while also maximising graphene production capability."

Both projects with Talga and Kibaran were supported by the Australian Government’s Innovation Connections program for small- to-medium-sized businesses.

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