Since first introduced by Claisse, twenty-five years ago, borate fusions have been used in XRF analysis of a wide variety of materials because fusion eliminates many of the problems associated with particle size and matrix effects encountered in the analysis of powders. Geological and environmental materials such as rocks, ores, sediments, slags, air-borne particulates, etc., lend themselves nicely to lithium or sodium tetraborate or lithium metaborate fusion because the inherent presence of silica in these materials stabilizes the resultant glass from crystallization.