Magnetic Susceptibility of Common Ore Minerals: A Reference Table

Magnetic susceptibility (χ) is the property that decides whether a mineral concentrates in a magnetic separator and at what field intensity. This page is a working reference for plant metallurgists and process engineers — minerals are grouped from strongly magnetic to diamagnetic, with the separator family that BAS typically recommends for each band. Specific susceptibilities vary with grain chemistry and oxidation state, so use this table as a starting map and confirm with sample-specific tests.

Susceptibility tiers and separator mapping

Read each tier as: representative minerals, qualitative susceptibility, and recommended separator family.

Tier 1 — strongly ferromagnetic

• Magnetite (Fe3O4) — strongly ferromagnetic. Recovery: dry/wet drum LIMS at 0.1–0.3 T. Recoveries 95–99% from coarse to fine when liberated.
• Pyrrhotite (Fe1−xS) — ferrimagnetic, variable. Recovery: medium-intensity drums at 0.3–0.5 T; some floats away from magnetite circuits.
• Maghemite (γ-Fe2O3) — strongly ferromagnetic, oxidation product of magnetite. Same routes as magnetite.
• Native iron (rare) — strongly ferromagnetic; trivial to recover with any drum or overband.

Tier 2 — strong paramagnetic

• Hematite (α-Fe2O3) — paramagnetic at ambient. Recovery: WHIMS at 1.0–1.5 T; dry roll at 1.0–1.4 T for fine cuts.
• Ilmenite (FeTiO3) — paramagnetic. Recovery: WHIMS or rare-earth roll at 0.8–1.4 T; standard in heavy-mineral sands.
• Chromite (FeCr2O4) — paramagnetic. Recovery: high-intensity wet or dry at 1.0–1.6 T after gravity pre-concentration.
• Wolframite ((Fe,Mn)WO4) — paramagnetic. Recovery: WHIMS at 1.0 T after gravity.
• Pyrolusite/Psilomelane (manganese oxides) — paramagnetic. Recovery: WHIMS at 0.8–1.2 T.

Tier 3 — moderate paramagnetic

• Garnet, Almandine — moderately paramagnetic. Recovery: rare-earth roll at 1.2–1.6 T.
• Biotite mica — moderately paramagnetic. Recovery: rare-earth roll, primarily in feldspar/mica plants.
• Tourmaline, monazite — moderate paramagnetic. Recovery: high-intensity dry roll for HM sand polishing.
• Rhodochrosite (MnCO3) — moderate paramagnetic. Recovery: WHIMS at 1.0–1.4 T.

Tier 4 — weak paramagnetic

• Siderite (FeCO3) — weakly paramagnetic. Recovery: WHIMS or rare-earth roll at 1.4+ T.
• Pyrite (FeS2) — weakly paramagnetic when oxidized; non-magnetic when fresh. Often floated rather than magnetically separated.
• Olivine — weakly paramagnetic. Specialty separation in industrial-mineral plants.
• Iron-stained quartz/feldspar — host is diamagnetic but iron coatings make particles weakly paramagnetic; rare-earth roll or WHIMS at 1.5 T removes color.

Tier 5 — diamagnetic / non-magnetic

• Quartz (SiO2) — diamagnetic. Reports to magnetic tails. Magnetic separation removes iron-stain only.
• Calcite (CaCO3) — diamagnetic. Same behavior as quartz.
• Feldspar (KAlSi3O8 series) — diamagnetic. WHIMS or rare-earth roll for iron impurity control.
• Kaolinite (clay) — diamagnetic; iron oxides as impurities are removed by WHIMS at 1.5+ T to meet ceramic/paper grades.
• Cassiterite, scheelite, sphalerite, galena, chalcopyrite — diamagnetic to very weakly affected; flotation or gravity is the right route, not magnetic.

Why this map is approximate

Two minerals with the same name can show different susceptibility values:

• Solid-solution chemistry — Fe3+ substitution into a mineral lattice changes susceptibility (e.g. Fe-bearing chromite is more magnetic than pure chromite).
• Oxidation state — Fe2+ vs Fe3+ behavior, hematite vs magnetite vs maghemite all differ.
• Particle size — fine grains may show stronger paramagnetic response per unit mass due to surface-bonded iron.
• Inclusions and locking — locked grains report based on the bulk particle, not the target mineral alone.

Always confirm susceptibility with a sample-specific Davis Tube test (for ferromagnetic) or a Frantz isodynamic test (for paramagnetic) before final equipment selection.

Separator selection by tier (cheat sheet)

1. Tier 1 (ferromagnetic) → dry magnetic drums / wet magnetic drums at 0.1–0.3 T.
1. Tier 2 (strong paramagnetic) → high-intensity wet electromagnetic separators or high-intensity roll magnetic separators at 1.0–1.6 T.
1. Tier 3 (moderate paramagnetic) → rare-earth roll separators at 1.2–1.6 T or specialty WHIMS.
1. Tier 4 (weak paramagnetic) → high-intensity wet electromagnets at 1.4–2.0 T; consider gravity pre-concentration.
1. Tier 5 (diamagnetic) → magnetic separation only for iron-stain removal; main concentration by flotation or gravity.

Lab and pilot support

BAS solution center runs Davis Tube, Frantz, lab WHIMS, and pilot dry roll separations on customer samples. Typical turnaround for a written test report with grade–recovery curves is 5–10 business days. The same lab supports flowsheet trade-offs between magnetic and complementary ore beneficiation plant routes.

Frequently Asked Questions

What is magnetic susceptibility?

Magnetic susceptibility (χ) measures how strongly a material magnetizes in response to an external magnetic field. Positive χ means paramagnetic or ferromagnetic (attracted); negative χ means diamagnetic (slightly repelled). In separation, χ determines the required field strength and the separator family.

Which is more magnetic, magnetite or hematite?

Magnetite (Fe3O4) is far more magnetic than hematite (Fe2O3). Magnetite is ferromagnetic and recovers at low fields (0.1–0.3 T); hematite is paramagnetic and needs high-intensity wet or dry separation at 1.0+ T.

Can I separate ilmenite from chromite magnetically?

Both are paramagnetic but with different susceptibilities. Selective separation is possible at intermediate fields (around 1.0 T), often combined with gravity and electrostatic separation in heavy-mineral sand circuits.

Is pyrite magnetic?

Fresh pyrite is essentially non-magnetic. Oxidized pyrite (transitioning toward goethite/hematite) becomes weakly paramagnetic. Most pyrite recovery is by flotation, not magnetic separation.

Does grain size affect magnetic susceptibility?

The intrinsic susceptibility is grain-size independent, but the apparent susceptibility per particle changes with size because of surface effects, locked vs liberated grains, and field reach. For practical separation, the size at which the mineral is liberated matters more than the size of the original ore.