In 1968 Consolidated Gold Fields commenced exploration below adit level at the Wheal Jane tin prospect in south-west England. During the surface exploration program the relatively recently introduced Portable X-ray Fluorescence Analyzer (“P.I.F.“) had been used for semi-quantitative scanning of drill core and for providing preliminary assays for tin on prepared core samples. The P.I.F. was introduced to the mining industry in 1965 (Bowie et. al. (1) and had originally been equipped specifically for tin analysis due to the current interest in tin exploration, the difficulties of chemically assaying for tin and the suitability of tin to X-ray analytical techniques. The instrumentation and principals of operation have been described by Bowie (1,2). At Wheal Jane the need to obtain rapid analyses to help control underground development and difficulties in visually recognizing the tin mineralization made the prospect an excellent testing ground for the practical aspects of the instrument.