THE ELECTRON microprobe analyzer (EMA) is an electron optical instrument that combines the imaging capabilities of light and electron microscopes with the analytical capabilities of X-ray spectrometers. With the electron beam rastered across the sample surface, the EMA can be used like a low-resolution scanning electron microscope, particularly to acquire backscattered electron images. With the electron beam focused to a small area on the sample surface, characteristic X-rays are generated for qualitative or quantitative analysis at micrometer-scale spatial resolution. Electron microprobe analysis is a routinely used, nondestructive technique for characterizing the compositions and compositional variations of minerals as well as other fine-grained materials.