While sampling fine-grain material we gathered it directly from opened wall with further concentration by water sieving. We took simultaneously maximum precautions against direct sunlight exposition, making all procedures under water layer not less than 30 sm. Models of radiometers, used by us, have the pointer indicator. The procedure of measurement included fixation of 30 momentary readings with interval of 10 sec. While sampling material from drill cores we tried to make the core maximum clear from surface material, which contains, as the rule, many dirty material from other layers.
Radiometric measurements present the special case when using drive pipes and clay mortar.
Drive pipes bring additional errors by means of screen effect, and clay substance brings additional radioactivity. We eliminated their influence with the help of empirical corrections when executing the works with drive pipes and clay mortars. Amount of the sample, required for qualitative analysis, depends upon content of quartz fraction with grain's size 0.1-0.25 mm. We are needed in guarantee for qualitative analysis that we shall get not less than 250 mg of pure quartz within mentioned size after all procedures. The ultimate end of laboratory preparation is separating from the sample monomineral quartz fraction with grain's size 0.1-0.25 mm.