At site rock and mineral measurement using a handheld Agilent FTIR analyzer

Importance of the Topic

FTIR spectroscopy enables rapid identification of minerals directly in the field, reducing sample preparation and accelerating decision making in geoscience applications. The development of a dedicated diffuse reflectance library enhances the accuracy of in situ analysis across diverse geological settings.

Objectives and Study Overview

This study aimed to establish a comprehensive rock and mineral spectral library optimized for handheld FTIR analyzers operating in diffuse reflectance mode. The work involved acquisition of representative spectra from igneous, metamorphic and sedimentary materials with varying chemical compositions and surface textures.

Methodology and Instrumentation

A diffuse reflectance sampling interface was employed to collect spectra from rock and mineral surfaces without preparation. Key steps included:

• Direct measurement of neat samples using a handheld FTIR system
• Acquisition of both rough and smooth surface spectra to account for specular components
• Spectral collection at 4 cm-1 resolution with 128 coadded scans, yielding results in approximately one minute

Instrumentation Used

• Agilent 4100 ExoScan FTIR analyzer
• Agilent 4200 FlexScan FTIR analyzer
• Diffuse reflectance sampling interface compatible with handheld FTIR

Main Results and Discussion

The custom library contained diffuse reflectance spectra for minerals across chemical classes such as sulfates, silicates and oxides. Inclusion of paired rough and specular spectra improved match quality. The on-board algorithm selects the best fit by comparing unknown spectra with both surface types. Continuous expansion ensures coverage of diverse geological compositions.

Benefits and Practical Applications

• On-site molecular composition analysis without grinding or KBr pellet preparation
• Rapid identification supports exploration, mining, core logging and environmental surveys
• Complementary to elemental analyzers, providing molecular insights
• User-defined library creation enables customization for specific field requirements

Future Trends and Opportunities

The diffuse reflectance FTIR approach is expected to evolve with larger field libraries, advanced pattern recognition algorithms and integration with remote sensing data. Emerging prospects include machine learning for automated classification and coupling with portable elemental sensors for comprehensive geochemical mapping.

Conclusion

The implementation of handheld FTIR with a dedicated diffuse reflectance library represents a significant advance for in situ geological analysis. By minimizing sample preparation and offering robust spectral matching, this technology empowers geoscientists with rapid, reliable mineral identification in diverse field environments.

Reference

• Alan Rein and Frank Higgins, Agilent Technologies Application Note, Publication Number 5990-7794EN, May 2011