Measured susceptibilities for rock types

rock type % of samples with magnetic susceptibility

(in 10⁻⁶ electromagnetic units per cubic centimetre)

less than 100 100–1,000 1,000–4,000 greater than 4,000

Basic extrusive (e.g., basalt) 5 29 47 19

Basic intrusive (e.g., gabbro) 24 27 28 21

Granite 60 23 16 1

Metamorphic (gneiss, schist, slate) 71 22 7 0

Sedimentary 73 19 4 4

Source: After D.H. Lindsley, G.E. Andreasen, and J.R. Balsley, "Magnetic Properties of Rocks and Minerals" in Handbook of Physical Constants, S.P. Clark, ed., Memoir 97, Geological Society of America, 1966, and L.B. Slichter, "Magnetic Properties of Rocks" in Handbook of Physical Constants, F. Birch, ed. (1942).