Top: BSE sample image with phases
identified by numbers (see text).
Bottom: Element map showing clearly
Simple phase differentiation tasks are often carried out using an electron microscope's BSE detector. In some cases this may fail, because density of phases is so similar that the image produces no contrast. This is where fast mapping is useful. Requiring only slightly more time, a wealth of information can be obtained, as the figures show: Where the naked eye can distinguish maybe three phases, mapping finds six.
The acquisition of this map with an resolution of 600 x 450 pixels took 300 s, using an input count rate of 220 kcps. The actual identification of phases was performed by evaluating spectra obtained from the differently colored areas. In this case the mineral proved to be consisting of calcium carbonate (no. 1 in the upper figure), a clay-altered silicate melt (2), calcium-magnesium phosphate (3), a sodium feldspar (4) and a potassium feldspar (5), all embedded in a quartz matrix (M).