7 - Applications in Earth, Planetary and Environmental Sciences

Abstract

As in many fields of natural science, the first step in a mineralogical, petrological or geochemical study is usually the examination, description and identification of an object. In the geological sciences the two classic techniques most often used for these operations are optical microscopy and X-ray diffraction. These techniques are often complemented by scanning or transmission electron microscopy, or by electron or ion microbeam analysis to obtain chemical compositions. However, even when they are used in combination, these techniques cannot, for several reasons, be applied successfully to all problems. Thus another microbeam method of investigation, which can yield a molecular fingerprint of the sample, and which can be used for the study of crystalline or amorphous materials, is necessary. These requirements are met by a new generation of Raman spectrometers, the Raman microprobes. Micro-Raman techniques can be easily applied to investigate the molecular vibrations of materials containing light elements. The phase identification for the characterization of a natural or synthetic rock sample in the environmental sciences is also discussed. In this particular application the micro-Raman spectroscopic measurements are performed on single microparticles with masses as small as 10–12 g. These samples are deposited on a suitable substrate, commonly either high-purity sapphire or lithium fluoride of single-crystal quality.