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RAMAN Spectroscopy: Rapid identification of lithium bearing minerals

Field identification of mineral phases within LCT pegmatite systems has been made simple with the handheld Bruker BRAVO Raman with duo laser excitation (Figure 1).

Bruker BRAVO Raman spectral instrument

Figure 1. Bruker’s handheld BRAVO Raman

What is Raman spectroscopy?

Raman is a form of vibrational spectroscopy that generates a spectrum by directing a monochromatic light from a laser onto a sample (Neuville et al., 2014). Most of the light scatters and remains at the same frequency, however a small percentage is absorbed and re-emitted as a process of vibrating (bending and stretching) the chemical bonds in the sample. The process changes the energy frequency of the incident light, and this subtle change in frequency is measured by the Raman spectrometer as Raman Shift. As the bonds within a sample are unique to that material, the generated spectrum is characteristic of that material and can be used for rapid identification, such as the identification of spodumene.

 

 

Raman’s Benefits

The application of Raman spectroscopy means there is no transport to expensive laboratories and no time-consuming analysis. The Bruker BRAVO Raman moves the lab into your hands, to the desired location and offers the most effective in-field non-destructive analysis. Mineral characterisation is achieved by verification or identification methods using Portable Spectral Services’ (PSS) Raman Spectral Pegmatite Library Database (PLD). To help combat the ever-growing lithium demand, the PLD helps to identify lithium bearing and associated minerals via spectral matching within minutes.

 

Identifying Opportunity

The application of Raman spectroscopy in earth sciences for qualitative mineral identification has been well documented by Dubessy et al., (2012) and Neuville et al., (2014). However, the technology has not yet been utilised in the mining industry. Therefore, many opportunities present itself to investigate the application of Raman at an industrial scale for rapid mineral identification.

Table 1 Common minerals found in LCT pegmatites.

Table 1 shows common minerals available in Raman Spectral Pegmatite Library Database. Bruker’s BRAVO Raman allows the user to build and manage libraries according to specific needs. For example, spectra of a single raw material present in various packaging can be stored in one comprehensive method separately. All methods are stored within a library that can be checked for consistency and signed. The Bruker BRAVO Raman can be used to perform direct analysis of drill core and chips in the field to provide identification of minerals that are visually challenging to identify, aiding decision making for further targeted analysis into key minerals of interest (Figure 2).

 

Raman provides a fast and more detailed alternative to aid visual identification, using either the Raman Spectral Pegmatite Library Database or a custom-built reference library. The rapid identification and verification of visually similar minerals e.g., white silicate, allows quicker synthesis of mineral zones while logging drill core (Figure 2 & 3).

Figure 2. BRAVO identified minerals rendered in 3D across Sinclair open pit.

Figure 3. Downhole data of an LCT pegmatite recorded with the BRAVO. 

The application of Raman spectroscopy in the exploration and mining industry compliments and enhances established methods for grade control and ore sorting. An exciting example of this was PSS’s application of portable Raman spectroscopy at Pioneer Resources’ discovery of pollucite (Pioneer, 2016) and the subsequent development of the Sinclair mine (Pioneer, 2018), providing a unique opportunity to test the application of Raman spectroscopy on an industrial scale alongside other spectral instrumentation. Raman was used in conjunction with pXRF for the high-density analysis of grade control blast hole samples. Li cannot be directly measured by pXRF which limits the ability to identify the Li zones during the grade control process.

Raman was able to identify the zones of Li-bearing silicates to complement the chemical data. The portability, robustness and rapid analysis time of both techniques enabled a comprehensive chemical and mineral map of the pit floor to be generated within a single working day that provided valuable information for ore extraction. Lithium has a big part in the future of mining in Australia. The combination of pXRF and RAMAN spectroscopy, allows geologists to validate these visually similar minerals seen in LCT pegmatites and create comprehensive databases instantly.

Learn More

Use of Raman spectroscopy in the discovery of Pioneer Resources Sinclair caesium deposit.

Portable Spectral Services application of Raman spectroscopy. 

Portable Spectral Services use of Raman spectroscopy in identifying LCT pegmatites such as spodumene. 

References

Dubessy, J., Caumon, M. C., and Rull, F., 2012, Raman spectroscopy applied to earth sciences and cultural heritage: The Mineralogical Society of Great Britain and Ireland.

Neuville, D. R., de Ligny, D., and Henderson, G. S., 2014, Advances in Raman spectroscopy applied to earth and material Sciences: Reviews in Mineralogy and Geochemistry, 78(1), 509-541.

Pioneer Resource Limited, 2016, Lithium-caesium discovery at Pioneer Dome.

Pioneer Resource Limited. 2018. Pioneer commences mining operations at Sinclair caesium mine.

Sinclair: Australia’s First Caesium Deposit: Discovery and Exploration Implications 

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