Mineral (Iron Ore)

Ironstone Concretion / Limonite Specimen

Goethite and Limonite (Hydrous Iron Oxides)

Gossan (with secondary copper minerals)

Iron-rich oxidized rock cap (Limonite/Goethite with Malachite/Chrysocolla inclusions)

Limonite (Iron Ore)

Goethite and related iron hydroxides (FeO(OH)·nH2O)

Limonite/Ironstone

Limonite (FeO(OH)·nH2O)

Ironstone Concretion (Limonite/Goethite)

Ferruginous Siltstone / Limonite Concretion (FeOO(OH)·nH2O)

Magnetite with Pyroxene

Magnetite (Fe3O4) in Mafic Igneous Matrix

Limonite-goethite ironstone specimen

Goethite (α-FeO(OH)) with limonite, quartz, and iron oxides

Limonite / Goethite Ironstone

FeO(OH)·nH2O (Hydrous iron oxide)

Limonite / Ironstone

Hydrated Iron Oxide (FeO(OH)·nH2O)

Hematite

Iron(III) oxide (Fe2O3)

Iron-stained Quartz

Silicon Dioxide with Iron Oxide (SiO2 + Fe2O3/FeO(OH))

Specular Hematite with Quartz

Ferric oxide (Fe2O3) and Silicon dioxide (SiO2)

Ironstone Concretion (Boxwork)

Siderite-Limonite Concretion (FeO(OH)·nH2O)

Weathered iron-rich rock, possibly limonite/goethite

Limonite (hydrated iron oxides; commonly goethite, FeO(OH), mixed with hematite)

Ironstone Concretion

Siderite or Hematite Concretion

Limonite (Iron-rich Siltstone / Sandstone base)

Hydrous ferric oxide mixture (FeO(OH)·nH2O)

Limonite Concretion (Ironstone)

Limonite (FeO(OH)·nH2O) with Goethite and Hematite

Iron-rich weathered stone, possibly hematite-rich ironstone

Hematite/goethite-bearing ironstone; predominantly Fe₂O₃ and FeO(OH)

Iron-rich weathered stone, possibly limonite/goethite

Limonite (mixture of hydrated iron oxides), commonly goethite (α-FeO(OH))

Limonite (Yellow Ochre)

Hydrated iron(III) oxide-hydroxides (FeO(OH)·nH2O)

Weathered iron-rich rock, possibly limonite-bearing basalt or ironstone

Undetermined; likely iron oxides/hydroxides (goethite–hematite–limonite) in a silicate host

Goethite (Iron Ore)

Goethite (FeO(OH))

Limonite (Iron Ore)

FeO(OH)·nH2O

Specular Hematite

Hematite (Iron(III) oxide, Fe2O3)

Specular Hematite (on Schist/Matrix)

Hematite (Alpha-Fe2O3)

Hematite

Hematite (Iron (III) oxide, Fe2O3)

Hematite

Hematite (Fe2O3)

Limonite (Iron Ore)

Hydrous ferric oxides (FeO(OH)·nH2O)

Chalcopyrite

Copper iron sulfide (CuFeS2)

Limonite Concretion

Hydrated Iron Oxide-Hydroxide, FeO(OH)·nH2O

Iron Slag

Anthropogenic Ferro-silicate

Limonite (Iron Ore)

FeO(OH)·nH2O (Hydrated Iron Oxide)

Lake Superior Agate

Cryptocrystalline Quartz (SiO2 with Iron impurities)

Tumbled Hematite

Iron(III) oxide (Fe2O3)

Ironstone Concretion

Ferruginous Sandstone / Siderite Concretion

Tumbled Hematite

Hematite (Alpha-Fe2O3)

Magnetite (Lodestone variety)

Magnetite (Fe3O4)

Unidentified dark mineral/rock fragment

Indeterminate; appearance may fit a sulfide-bearing rock or iron-rich mineral

Limonite (Gossan)

FeO(OH)·nH2O (Hydrated Iron Oxide)

Limonite with Quartz (Gossan)

Hydrated iron(III) oxide-hydroxide mixture (FeO(OH)·nH2O) with Silicon Dioxide (SiO2)

Hematite

Iron(III) oxide (Fe2O3)

Limonite (Iron Ore)

Limonite (Hydrated iron(III) oxide-hydroxide, FeO(OH)·nH2O)