This crossplot is used to to identify clay types from thorium to potassium ratios. Heavy thorium-bearing minerals, glauconite, mica and feldspar can also be identified with this crossplot.
Start by inputting potassium-thorium data series, (green, blue and orange cells). Each data series allows an unlimited number of rows, and cut and paste functionality is available. Potassium is in percent and thorium is in parts-per-million.
After data are loaded, review the spatial distribution of each series to identify the clay type / radioactive minerals present.
Schlumberger's Industry Publication, "Log Interpretation Charts." CP-19 Chart from 2000 Edition.