**Petrographical and Mineralogical Applications of Raman Mapping Provisional chapterPetrographical and Mineralogical Applications of Raman Mapping**

Frédéric Foucher, Guillaume Guimbretière, Nicolas Bost and Frances Westall Frédéric Foucher, Guillaume Guimbretière, Nicolas Bost and Frances Westall

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/65112

#### **Abstract**

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162 Raman Spectroscopy and Applications

Raman spectroscopy has undergone rapid development over the last few decades. The ability to acquire a spectrum in only a few tens of milliseconds allows use of Raman mapping as a routine technique. However, with respect to classical single spectrum measurement, this technique is not still as widely used as it could be, in particular for mineralogy and petrography. Here, we explain the advantages of Raman mapping for obtaining additional information compared to single spot analyses. The principle and the limits of the technique are first explained in 2D and 3D. Data processing techniques are then described using different types of rocks and minerals to demonstrate the utility of Raman mapping for obtaining information about the general composition, identifi‐ cation of small phases, as well as for distinguishing minerals that are spectrally very close. More "exotic" uses of the collected signal are also described. Finally, a gallery of images from representative samples is used to illustrate the discussion.

**Keywords:** Raman mapping, petrography, mineralogy

## **1. Introduction**

The Raman effect was described for the first time by Chandrasekhara Venkata Rāman in 1928. Raman spectroscopy is a very powerful technique allowing study of atomic bonds and identification of crystalline structures. Contrary to energy dispersive X‐ray spectroscopy (EDX) or the electron microprobe, for example, Raman does not give the elemental composition of the sample but can identify organic molecules and mineralogical phases. No sample preparation is required, and the analysis can be made on the sample surface or below the surface, depending

© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

on sample transparency. For technical reasons, the technique began to be widely used only at the beginning of the 1980s with the generalisation of lasers. At the end of the 1990s, Raman spectroscopy underwent a second phase of development with the introduction of Charge Couple Device (CCD) technology, which has widely improved the sensitivity of spectrometers. These technical revolutions allow acquisition of a Raman spectrum in only few milliseconds. This strong decrease in the acquisition time permitted development of new applications, in particular Raman mapping. This technique consists of scanning the sample with the laser while acquiring spectra so that spatial distribution can be added to structural information.

Here, we present the principle of the technique and the basis of the associated data processing followed by an overview of the information that can be extracted from Raman mapping to improve mineralogical and petrological analyses. In particular, we discuss how it can be used to study the general composition of rocks, to detect and identify small phases, or to differentiate minerals whose spectra are very close. More exotic uses of the collected signal are also presented, e.g., detection of particular phases using luminescence. Finally, we illustrate the discussion using a number of different types of rocks and minerals.
