Mineral Microbeam Analysis
Mineral microbeam analysis (MMA) is a microscopic technique used to identify and determine the composition of minerals. While the technique has been used in the geological sciences for many years, the advances in electron microscopes and the availability of analytical software have made MMA a more accessible tool.
The MMA technique focuses on the properties unique to individual mineral grains which are used to identify what type of mineral is present and its chemical composition. Two of the most common microbeam techniques used in MMA are electron backscatter diffraction (EBSD) and electron microprobe analysis (EMPA). EBSD maps the sample by recording the intensity and diffraction patterns of electrons that recoiled off the crystallographic structure of a mineral while EMPA maps the sample composition by measuring the energy and depth of characteristic x-rays emitted from the sample when exposed to an electron beam.
Using critical data from these two techniques, the mineral type and chemistry of the sample can be determined. The results of an MMA analysis can be used to deduce the original environment of deposition for the sample, for comparison between mineral samples, and for applications in resource exploration and exploitation.
Compared to more traditional methods of mineral analysis, MMA has several advantages. The technique is much more accurate, partial data from one part of a mineral grain can be used, and the technique has a greater sample area than the previous methods. Further, the technique is much less damaging to the mineral sample, making it possible to work with very small samples, while still providing large amounts of data.
In the age of rapid technological development, MMA provides a simple, inexpensive, and accurate way to quantify the properties of a mineral sample. The data produced by the technique is easily accessible and interpretable; and, with the constant improvements in instruments, software, and analytical techniques, MMA will remain an invaluable resource for geologists and mineral scientists alike.
