Is goethite magnetic?
Is goethite magnetic? Not like magnetite: its sheet prints no magnetism, and USGS pulled 6 samples at 0.20–0.70 amp. 62.85% iron, yet less pull than siderite.
Not like magnetite. The Handbook sheet for goethite, FeO(OH), hardness 5–5.5, prints no magnetic property, and USGS Open-File Report 99-529 pulled 6 goethite samples on a laboratory separator at 0.20 to 0.70 amp, best 0.40 to 0.50: paramagnetic by its definitions, where magnetite came off at 0.01. Goethite is 62.85% iron, yet pulls less than siderite.
In short
- Two sources, one answer. The Handbook of Mineralogy goethite sheet gives α-Fe3+O(OH), orthorhombic, hardness 5–5.5, density 4.28 and a brownish yellow to ocher-yellow streak, and no magnetic property. USGS Open-File Report 99-529, Table 1 gives goethite, 6 samples, at 0.20–0.70 amp, best 0.40–0.50: inside the report’s paramagnetic range, which runs to 1.70 amp. Magnetite’s best range was 0.01.
- The goethite inversion. We matched 10 iron minerals in Table 1 to IMA formulas and worked their iron by mass. Goethite, at 62.85%, has the third-most iron, behind magnetite (72.36%) and hematite (69.94%), yet its best range, 0.40–0.50 amp, is the highest of the ten, shared with jarosite (33.45%) and ankerite (25.86%). siderite, 48.20% iron, came off at 0.20–0.30.
- The three FeO(OH) sheets agree in silence. Goethite is trimorphous with lepidocrocite and feroxyhyte, both FeO(OH) on the IMA list. A script over the three Handbook sheets finds no magnetic wording on any of them. Silence is absence from the source, not a measured zero, and Table 1 has no lepidocrocite or feroxyhyte row.
- Documented failure: a pull is about something else. the USGS report says magnetite micro-inclusions make a lower extraction limit difficult or impossible to determine, and that weathered minerals or alteration products may extend the upper limit. The maghemite sheet lists goethite among its associates and calls maghemite strongly magnetic. A goethite that snaps to a hand magnet is telling you about another mineral in it.
- Iron oxide, rust, secondary? The IMA formula is FeO(OH): an iron oxide-hydroxide, not the oxide Fe2O3, which is hematite. The sheet calls goethite a common weathering product of iron-bearing minerals in oxygenated environments, and also a primary precipitate in hydrothermal, marine and bog settings. It never uses the word rust, and nor does any source fetched here.
| Mineral | IMA formula | Iron by mass, worked | Iron rank | USGS total range, amp | USGS best range, amp | Samples | Handbook magnetic wording |
|---|---|---|---|---|---|---|---|
| Magnetite | Fe2+Fe3+2O4 | 72.36% | 1 | Below 0.01–0.05 | 0.01 | 6 | Strongly magnetic |
| Hematite | Fe2O3 | 69.94% | 2 | 0.025–0.50 | 0.10–0.30 | 11 | None printed |
| Goethite | FeO(OH) | 62.85% | 3 | 0.20–0.70 | 0.40–0.50 | 6 | None printed |
| Fayalite | Fe2+2(SiO4) | 54.81% | 4 | 0.10–0.60 | 0.20–0.30 | 2 | None printed |
| Siderite | Fe(CO3) | 48.20% | 5 | 0.10–0.50 | 0.20–0.30 | 17 | None printed |
| Ilvaite | CaFe3+Fe2+2O(Si2O7)(OH) | 40.98% | 6 | 0.10–0.50 | 0.30 | 5 | None printed (the word occurs only in a reference title) |
| Ilmenite | Fe2+Ti4+O3 | 36.81% | 7 | 0.025–0.40 | 0.20–0.30 | 8 | Weakly magnetic |
| Jarosite | KFe3+3(SO4)2(OH)6 | 33.45% | 8 | 0.20–0.60 | 0.40–0.50 | 3 | None printed |
| Ankerite | CaFe2+(CO3)2 | 25.86% | 9 | 0.30–0.70 | 0.40–0.50 | 1 | None printed |
| Hedenbergite | CaFe2+Si2O6 | 22.51% | 10 | 0.10–0.50 | 0.20–0.40 | 6 | None printed |
Is goethite magnetic? What the sheet and the separator record
Goethite is paramagnetic on a laboratory separator and has no magnetic property on its reference sheet. The Handbook of Mineralogy goethite sheet gives α-Fe3+O(OH), orthorhombic, prismatic crystals striated ∥ [001] to 45 cm or tabular on {010}, more commonly capillary sprays or reniform, botryoidal and stalactitic masses, nearly cryptocrystalline in “limonite”. Hardness 5–5.5, density 4.28 measured, streak brownish yellow, yellow-orange or ocher-yellow. It is silent on magnetism; the IMA list gives FeO(OH), status A, 1980 s.p., Germany.
The measurement. USGS Open-File Report 99-529, Magnetic Susceptibilities of Minerals (Rosenblum and Brownfield) passed dry 125 to 150 µm grains through a Frantz isodynamic separator at a 15° side tilt. Goethite, 6 samples, came off at 0.20 to 0.70 amp, best 0.40 to 0.50, and Table 1 does not flag it as often locked with other species, as it does hematite and magnetite. The report defines ferromagnetic minerals as strongly attracted to a magnet, like a piece of iron, naming magnetite, maghemite, pyrrhotite and pentlandite; paramagnetic minerals as less magnetic than that and separable at up to 1.70 amps; and diamagnetic minerals as nonmagnetic at 1.70 amps. Goethite is on the paramagnetic side. Neither source tests a hand magnet, so this page predicts nothing about one.
On this site. The goethite species page gives the same hardness, density and streak. The separator comparison between hematite and magnetite is on is hematite magnetic, which lists goethite’s row in passing; its ten-times comparison is not repeated here.
More iron, less pull: the goethite inversion
Goethite carries more iron than siderite but needs more current to be pulled. Method: we took the iron minerals with both a Table 1 row and a Handbook sheet used on these pages, matched each by name to the September 2026 IMA list, and worked iron by mass from the IMA formula on standard atomic weights. That gives 10 rows. Ranked by iron, goethite is third, at 62.85%, behind magnetite at 72.36% and hematite at 69.94%. Ranked by best-range current, goethite’s 0.40–0.50 amp is the highest of the ten, level with jarosite at 33.45% iron and ankerite at 25.86%. Fayalite (54.81%) and siderite (48.20%), with less iron, came off at 0.20–0.30.
What USGS says about iron. The report says iron substituting for calcium or magnesium is the best example of a metal changing susceptibility, and that iron-bearing carbonates are more magnetic than iron-free ones; that comparison, across the carbonates, is on is siderite magnetic. It does not say that more iron means more pull across different structures, and these ten rows show it does not: goethite sits level with iron-poor ankerite and jarosite, while fayalite and siderite, with less iron than goethite, were pulled at lower current. The rule is a description of these 10 rows, not a law.
Documented failure: limonite. The goethite sheet uses “limonite”, in quotation marks, for nearly cryptocrystalline goethite. the USGS report says nonmagnetic weathered minerals or alteration products may extend the upper limit of extraction. Goethite is itself a weathering product on its sheet, so earthy brown material labelled limonite may read anywhere on the separator. The six Table 1 samples are goethite; they are not a measurement of limonite. Ilmenite, the only iron mineral of the ten besides magnetite whose sheet prints a magnetic word, is on is ilmenite magnetic.
Why might a goethite specimen pull a magnet?
A strong pull points to a ferromagnetic mineral in the piece, on USGS’s definitions. The report says that when micro-inclusions of magnetite or other ferromagnetic minerals are present it is difficult or impossible to determine a mineral’s actual lower limit of extraction. The goethite sheet lists lepidocrocite, hematite, pyrite, siderite, pyrolusite and manganite among its associates, and many other iron- and manganese-bearing species. The maghemite sheet lists goethite among maghemite’s associates, calls maghemite strongly magnetic, and says it forms by weathering or low-temperature oxidation of spinels with ferrous iron, commonly magnetite.
The three FeO(OH) minerals. The goethite sheet says goethite is trimorphous with feroxyhyte and lepidocrocite; the IMA list writes both of those Fe3+O(OH). The lepidocrocite sheet gives hardness 5, density 4.09 and a dull orange streak; the feroxyhyte sheet, density 4.20 calculated, says it transforms in air to goethite. A script over all three sheets finds no magnetic wording, and Table 1 has rows for neither lepidocrocite nor feroxyhyte, so this page says nothing more about their magnetism.
Without a magnet. The streak separates the iron oxides better than the magnet does: brownish yellow to ocher-yellow for goethite, dull orange for lepidocrocite, cherry-red or reddish brown for hematite and black for magnetite, all on their sheets. The method is on how to use a streak plate. At 4.28 a 20.00 g goethite reads 15.33 g in water, against 16.20 g for hematite and 16.14 g for magnetite. The meteorite question, where these three often turn up, is on is my rock a meteorite.
Is goethite an iron oxide, rust or a secondary mineral?
Iron oxide: in the broad sense, yes; strictly it is an oxide-hydroxide. The IMA formula FeO(OH) contains only iron, oxygen and hydroxyl, with no carbonate, sulfate or silicate. Worked, it is 62.85% iron; the sheet’s El Paso County, Colorado analysis, Fe2O3 89.65%, gives 62.70%. The anhydrous iron oxides are hematite, Fe2O3, and magnetite, Fe2+Fe3+2O4. Whether goethite counts as an ore is on is siderite an ore of iron.
Secondary mineral: usually. The sheet’s Occurrence field reads: a common weathering product derived from numerous iron-bearing minerals in oxygenated environments; an important component of ore in weathered iron deposits; also a primary precipitate in hydrothermal, marine and bog environments upon oxidation of reduced iron-bearing waters. So most goethite is secondary, and some is not.
Rust and clay. Neither the sheet nor the IMA row nor the USGS report uses the word rust, and no source fetched for this page defines rust, so this page does not equate the two. Nor does any of them call goethite a clay mineral; its formula has no silicon or aluminium. The magnet survey across the site is on which minerals are magnetic, and the identification guides are in the collecting guides. Nothing on this site is offered for sale; the wanted list is the only commercial route.