Rock Type

Potassium-40

Thorium-232

Uranium-238

Total K (%)

Bq∙kg⁻¹

ppm

Bq∙kg⁻¹

ppm

Bq∙kg⁻¹

Igneous rocks

Crustal average

0.8

300

3 to 4

10 to 15

0.5 to 1

7 to 10

Mafic

0.3 - 1.1

70 - 400

1.6 - 2.7

7

0.5 - 0.9

7

Salic

4.5

1100 - 1500

16 - 20

60

3.9 - 4.7

50

Granite (crustal aver.)

≤4

≤1000

17

70

3

40

Sedimentary rocks

Shale, sandstones

2.7

800

12

50

3.7

40

Clean quartz

≤1

≤300

≤2

≤8

≤1

≤10

Dirty quartz

2

400

3 to 6

10 to 25

2 to 3

40

Arkose

2 to 3

600 - 900

2

≤8

1 to 2

10 to 25

Beach sands

≤1

≤300

6

25

3

40

Carbonate rocks

0.3

70

2

8

2

25

All rock (range)

0.3 - 4.5

700 - 1500

1.6 - 20

7 to 80

0.5 - 4.7

7 to 60

Continental crust (ave.)

2.8

850

10.7

44

2.8

36

Soil (ave.)

1.5

400

9

37

1.8

22