Mineral, Specifically An Iron Ore

Limonite (Ironstone Concretion)

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

Green Calcite

Calcite (Calcium Carbonate, CaCO3)

Sandstone (Ferruginous)

Clastic sedimentary rock (SiO2 with Fe2O3)

Iron-rich weathered rock, possibly limonite/goethite-bearing breccia

Limonite (FeO(OH)·nH₂O), goethite (α-FeO(OH)), and iron oxides; host uncertain

Ironstone (iron-oxide-rich rock)

Ferruginous sandstone or ironstone; likely composed chiefly of goethite and/or limonite, with quartz and clay

Likely brown ironstone or limonite-rich rock fragment

Ironstone, chiefly iron oxides/hydroxides such as goethite (α-FeO(OH)) and limonite

Hematite

Iron(III) oxide (Fe2O3)

Hematite (specular hematite)

Hematite, α-Fe₂O₃ (iron(III) oxide)

Specular Hematite Geode/Nodule

Specularite (Polycrystalline Hematite), Fe2O3

Weathered iron-rich rock, possibly limonite-bearing sandstone or laterite

Goethite–hematite (FeO(OH)–Fe₂O₃) in a silicate-rich matrix; exact identification requires testing

Goethite (Iron Ore)

Goethite (FeO(OH))

Limonite (Iron Ore)

Hydrous ferric oxides (FeO(OH)·nH2O)

Hematite

Iron(III) oxide (Fe2O3)

Goethite/Limonite Iron Ore Node

Goethite (FeO(OH)) or Limonite (mixture of hydrated iron oxides)

Hematite

Hematite (Fe2O3)

Hematite

Iron(III) oxide (Fe2O3)

Amethyst (Chevron Amethyst)

Silicon Dioxide (SiO2) with iron impurities

Orange Calcite

Calcium Carbonate (CaCO3)

Bauxite

Bauxite (mixture of Hydrous Aluminum Oxides)

Limonite (Iron Ore)

Hydrated ferric oxide (FeO(OH)·nH2O)

Specularite in Quartz

Specular Hematite (Fe2O3) in Quartz (SiO2)

Banded iron formation fragment (likely hematite–magnetite ironstone)

BIF; chiefly hematite (Fe₂O₃), magnetite (Fe₃O₄), and silica as microcrystalline quartz (SiO₂)

Ironstone Concretion

Siderite or Limonite Concretion (FeCO3 or FeO(OH)·nH2O)

Jasper Breccia

Silicon Dioxide (SiO2) with iron inclusions

Yellow Ochre (Limonite)

Limonite (FeO(OH)wH2O)

Mahogany Obsidian

Volcanic Glass (SiO2 with Hematite/Magnetite inclusions)

Iron (Hematite variety)

Iron (Fe) / Hematite (Fe2O3)

Tumbled hematite

Hematite (iron(III) oxide, Fe₂O₃)

Amethyst (specifically Chevron Amethyst or Dream Amethyst)

Silicon Dioxide (SiO2) with iron impurities

Limonite

Hydrous Iron Oxide (often Goethite FeO(OH), Lepidocrocite γ-FeO(OH), and other amorphous iron oxyhydroxides)

Jasper (specifically Yellow or Bumblebee-like Jasper)

Silicon Dioxide (SiO2) with impurities

Likely pyrite-bearing rock fragment

Pyrite (FeS₂), possibly in a weathered host rock; identification is uncertain from the image

Fossiliferous Concretion

Septarian Concretion containing Brachiopods/Crinoids

Ironstone Concretion

Siderite or Hematite Concretion

Weathered iron-rich rock, likely limonite/goethite-bearing basalt or ironstone

Limonite (hydrated iron oxides; chiefly goethite, FeO(OH)) with probable silicate host rock

Limonite Concretion

Limonite (FeO·nH2O)

Ironstone (Limonite/Hematite concretion)

Ferruginous Siltstone / Goethite (FeO(OH))

Iron-rich sandstone or limonite/goethite concretion

Ferruginous sandstone with limonite–goethite (hydrated iron oxides), possibly a weathered ironstone concretion

Green Common Opal

Hydrated Silica (SiO2·nH2O)

Chert / Jasper

Microcrystalline Quartz (SiO2)

Iron-rich weathered rock, possibly laterite or ironstone

Ferruginous laterite/ironstone; primarily goethite (FeO(OH)) and hematite (Fe₂O₃), with clay minerals

Red Jasper with Quartz

Microcrystalline Quartz (SiO2)