X-RAY FLUORESCENCE ANALYSIS OF SAW CUTTINGS OF GRANITIC ROCKS

We have compared the elemental composition of granitic rocks obtained by means of x-ray fluorescence (XRF) measurements on powdered samples with results obtained by means of inductively coupled plasma-mass spectrometry (ICP-MS) analysis of digested rock samples to assess an easy method of sample preparation for XRF. XRF analysis requires that the sample be finely powdered to a particle size of 200 microns or less. Producing a uniform, finely powdered sample of a hard rock such as granite or gneiss can be problematic. Samples can be hammered to a fine powder, but this is difficult to do by hand and automated equipment for that purpose is expensive. We have used a relatively inexpensive tile saw with a wet cut (water-cooled) continuous rim diamond blade of the type commonly used to cut ceramic tile. The cuttings were collected in the basin of the saw which served as a water reservoir. Several cubic centimeters of the rock were ground up by the blade and the cuttings were collected and dried. The samples were prepared for XRF by placing the sieved powders in sample cups of the type used for soils. In this study, a measure of the efficacy of this sample preparation method was obtained by comparing the XRF results with results obtained by ICP-MS analysis of digested rock samples.