Enhanced quantification of wollastonite and calcite in limestone using fluorescence correction based on continuous wavelet transformation for Raman

Abstract

Raman spectroscopy offers a nondestructive means to identify minerals in rocks, but the ability to use the technology for quantitative mineralogical analysis is limited by fluorescence that can mask the spectral features of minerals. In this paper we apply continuous wavelet transformation (CWT) to remove fluoresence from Raman data acquired from 26 carbonate rock samples. We then record the intensity values of individual spectral features, proxies for mineral abundances, using the original Raman data and the thus inferred CWT data. The intensity values are then compared against the known mineral abundances determined using the scanning electron microscope (SEM) technology. This comparison is conducted using a linear regression model to determine whether fluorescence removal enhances the mineral abundance predictions. Our results suggest that CWT enhances the accuracy of mineral abundance estimates, thus highlighting the importance of fluorescence removal when using Raman for quantitative mineralogical analysis.

Keywords:

• Raman
• fluorescence
• wavelets
• wollastonite
• calcite

Acknowledgements

The authors are indebted to Mr. Markku Lehtinen for his invaluable help with the sample collection, and for generously sharing his abundant knowledge of the study area. The authors would also like to thank Dr. Sari Lukkari and Dr. Bo Johanson from the Geological Survey of Finland for their help with the scanning electron microscope data acquisition.

Disclosure statement

The authors report no potential conflicts of interest.

Additional information

Funding

This work was supported by the Mineral Resources and Material Substitution program (project: New laser and spectral field methods for in situ mining and raw material investigations) by the Academy of Finland.