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Smithsonian National Museum of Natural History
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Department of Mineral Sciences

Izalco Volcano

The electron microprobe is mostly used for WDS and EDS quantitative analysis of major and minor elements of minerals and glasses. Volumes as small as 1 micron (10-6 m) diameter can be analyzed. Occasionally museum specimens from other departments or from other museums are analyzed. In the order of 10,000 quantitative analyses are performed per year. A large proportion of the analyses are performed on minerals and glasses from volcanic rocks.

X-ray maps from the WDS and the EDS are used to examine the two-dimensional distribution of elements on a specimen surface. Up to 20 elements can be specified for measurement on each analysis area. Measurement can be made in two modes, stage scanning and beam scanning. A raw-data map of X-ray intensity can be converted into a concentration map using calibration curves. Functions available for two-dimensional data include simple image processing such as various arithmetic operations and smoothing, line profile display, and analytical functions such as distance measurement.

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