Gamma Ray Emission (GR)

Natural Gamma Ray emission from subsurface rocks

Table 1. Typical GR values for popular minerals
	Rock Type	GR, GAPI
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

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