The XRF would have been used to guide visual estimates of nickel...

The XRF would have been used to guide visual estimates of nickel bearing sulphides in the chip samples by the geologist. E.g. zap a few chips, realize the brown looking sulphide/s are carrying nickel, there is approx. 4% of these brown disseminated sulphides in the sample and 30% of sulphides are composed of element nickel (the rest is Fe, S Co etc) so the visual estimate of grade for this sample is about 1.2% Ni (30% of 4%). You can zap as many chips as you like and average but unless the sample is homogeneous your going to get an incorrect result. Although it would be nice to zap a lot of chips to increase the confidence of visual estimations and get a ballpark figure of grades. Labs use XRF but crush & pulverize & split the sample to get a representative sample prior to zapping it. XRF in the field is used by geo's to help guide them in mineral identification and hence visual grade estimations. Its also used to help vector into MZ by looking at mineral assemblages and figuring out where you might be in a MZ system. If its being used to directly estimate grade its probably not a geo doing it, probably the MD zapping the shiny bits. Good geos will get close to the real grade by visual estimation, confidence goes up with the geos experience and especially ****relevant experience**** with the deposit type. I have no idea what RXL have done, this is just what rock lickers usually do with an XRF gun.