Portable x-ray fluorescent (XRF) analyzers have proven to be accurate elemental analyzers and are currently used extensively in the mining industry worldwide. However, are they appropriate for Uranium –Thorium (U-Th) exploration? An investigation was carried out in the Nopal area, northeast Mexico by SGM (Servicio Geologico Mexicano) geologists. A total of 1,334 samples were analyzed systematically in 31 stations on 40 linear sections with 100 m spacing. Uranium content of each sample was measured by radiometric method, laboratory analysis, and field portable XRF on prepared samples. For the radiometric method, scintillometers were used. These instruments are commonly used for U-Th exploration and some models can provide semi-quantitative data. The geochemical maps of U, based on these three methods, were prepared and are shown in this uranium application note . As Figure 1 on the application note shows, there is a very good overlap between geochemical anomalies of U identified by lab and field portable XRF. Also Th from XRF assays shows the same anomalies as U. Laboratory Th data were not available for comparison. Although scintillometers are very effective tools for fast identification of radioactive samples, their data may not be as reliable as lab or portable XRF assays because their U and Th anomalies do not overlap with those from lab or portable XRF assays. Such instruments can be more effective if used in conjunction with field portable XRF in the field. Is there a certain element that you are uncertain about regarding the successfulness of XRF analysis? Just let us know and we will try to address that element in future postings.