Preparation of micro- and crypto-tephras for quantitative microbeam analysis

The smallest tephra grains present special challenges in their preparation for quantitative microbeam chemical analysis by EPMA and LA-ICP-MS. High-quality polished surfaces are an essential pre-requisite for the collection of high quality quantitative chemical data, as these shards also present significant difficulties for analysis. A method for the preparation of tephra grains as small as 10-50 mu m is described in detail. This method uses inexpensive, widely available materials and is easily implemented in facilities in which polished geological samples are prepared for microanalysis. Samples prepared in this way reduce or eliminate the difficulties in microbeam analysis associated with small grains, when appropriate analytical protocols are used.