Natural Gamma Ray emission from subsurface rocks
The typical GR values for popular minerals is brought on Table 1Table 1. Typical GR values for popular minerals Rock Type GR, API 1 Halite (Rock Salt) 0 2 Coal 0 3 Limestone 5 – 10 4 Sandstone 10 – 20 5 Dolomite 10 – 20 6 Shale 80 – 140 7 Mica 100 – 170 8 Sylvite (KCl) 500