Determination of the composition of gems by Raman Spectroscopy (CAT#: STEM-ST-0086-WXH)

Introduction

In many cases, gems belong to a mineral group which constitutes an isomorphic series whose chemical composition changes continuously within a specified range. The extreme terms of the compositional range are the so-called end members of the series and, in general, every member of the group can be considered a solid-state solution of the end members. Tourmalines and garnets are examples of gems which do not correspond to mineral species but to mineral groups. Knowledge of the actual composition of a gem, which could be expressed as the percentage of the various end members of the group, is important to give a correct estimation of its value and provenance.