Typical magnetic properties of rocks

rock J_n

natural remanent magnetization (10⁻⁵ electromagnetic units per cubic centimetre) k

magnetic susceptibility (10⁻⁵ electromagnetic units per cubic centimetre) ratio*

Q_n=J_n/k·H_ex

Igneous

granite 10–80 50–400 0.3–1

diabase 190–400 100–230 2–3.5

basalt 200–1,000 100–700 5–10

seafloor basalt (1–6 metres) 500–800 30–60 25–45

typical (average) 10–4,000 5–500 1–40

Sedimentary

red sediments 0.2–2 0.04–6 2–4

sandstone 1–40

shale 1–50

limestone 0.5–20

typical (average) 0.1–10 0.3–30 0.02–10

Ores

magnetite ore 300,000–1,000,000 30,000–100,000 ~10–50

hematite ore 10–70

*For external magnetic field (H_ex) = 0.5 oersted, the cgs electromagnetic unit of magnetic field intensity.

Source: After Robert S. Carmichael, ed., Handbook of Physical Properties of Rocks, vol. II, CRC Press, Inc. (1982).