Abstract SIMS (secondary-ion mass spectrometry) is an analytical technique for the surface, near-surface, and bulk characterization of solids. The technique uses a primary beam of ions to sputter a sample surface, producing a secondary beam of ionized particles (secondary ions) that are passed through a mass spectrometer. Acquired data may be presented as mass spectra, depth profiles showing element concentrations or isotope ratios, and ion images. SIMS has a number of advantages over electron-beam and X-ray analytical techniques. Secondary-ion intensities can be measured over a dynamic range of nine orders of magnitude (vs. two orders of magnitude for AES and XPS). All elements may be detected, and their isotopes distinguished. Detection limits range from ppm to ppb. Depth profiling and ion imaging are possible, with excellent depth and lateral resolution. Because of the low detection limits that may be obtained with SIMS, this technique is invaluable for the quantification of precious metals, which commonly occur in very low concentrations. In addition, the depth- profiling and imaging capabilities of SIMS reveal whether metals are present as submicroscopic inclusions or are dispersed throughout the matrix; this information is important for maximizing the efficiency of mineral processing. Figure 1 shows a schematic of the ion optical system for the Cameca ims 4f ion microprobe. Primary ions are produced in a duoplasmatron or cesium source, then extracted, mass filtered and accelerated by a high voltage (10-30 kV).