Mineral, Specifically An Iron Ore

Black Tourmaline

Schorl (Sodium Iron Aluminum Borosilicate Hydroxide)

Druzy Quartz on Sandstone

Silicon Dioxide (SiO2) on Sedimentary Host Rock

Botryoidal hematite/goethite specimen

Hematite (Fe₂O₃), likely with goethite (FeO(OH)) and minor limonite

Limonite (Iron Ore)

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

Botryoidal Goethite

Goethite (α-Fe3+O(OH))

Limonite Pseudomorph after Pyrite

Goethite/Limonite FeO(OH)·nH2O replacing Pyrite FeS2

Quartz (likely Rose Quartz or Milky Quartz)

Silicon Dioxide (SiO2)

Iron-rich rock, possibly ironstone

Likely ferruginous sandstone or ironstone; exact identification requires testing

Banded ironstone (likely jasper-rich ironstone)

Iron-rich chert/jasper with iron oxides, chiefly hematite and goethite; exact identification requires testing

Polished hematite (possibly specular hematite)

Hematite, α‑Fe₂O₃

Hematite Nodular Concretion

Iron(III) oxide (Fe2O3)

Possible hematite-bearing pebble

Hematite, Fe₂O₃, possibly mixed with magnetite or iron-rich matrix

Likely tumbled black stone or glassy mineral

Indeterminate from image; possibilities include obsidian, hematite, or black tourmaline

Iron-rich goethite/limonite specimen

Goethite, α-FeO(OH), commonly mixed with limonite and other iron oxides

Specular Hematite

Hematite (Fe2O3)

Hematite

Hematite (Fe2O3)

Citrine Quartz

Silicon Dioxide (SiO2) with iron impurities

Citrine

Silicon Dioxide (SiO2) with iron impurities

Hematite Ball

Iron(III) oxide (Fe2O3)

Ironstone / Hematite

Iron(III) oxide (Fe2O3)

Orange Calcite (Iron-Stained)

Calcium Carbonate (CaCO3)

Tumbled chalcedony (likely milky agate)

Microcrystalline quartz, SiO₂ (chalcedony)

Rounded ironstone concretion

Iron-rich sedimentary concretion, commonly composed of goethite and/or hematite cementing sand or clay

Iron-rich slag or ironstone; appearance is not diagnostic

Likely iron-oxide-rich material (hematite, Fe₂O₃, and/or magnetite, Fe₃O₄); possibly smelting slag

Chalcopyrite

Copper iron sulfide (CuFeS2)

Limonite (Iron Ore)

Limonite (FeO(OH)·nH2O)

Citrine

Citrine (Silicon Dioxide, SiO2)

Banded Iron Formation (BIF) or similar banded sedimentary rock

Banded Iron Formation

Bauxite

Bauxite (Al(OH)3, AlO(OH))

Hematite (or Magnetite iron ore gravel)

Hematite (Fe2O3) / Magnetite (Fe3O4)

Specular Hematite (Specularite)

Hematite (Fe2O3)

Hematite

Hematite (Α-Fe2O3)

Limonite (Oxidized Iron Ore)

FeO(OH)·nH2O (Hydrous ferric oxide)

Limonite (Iron Ore)

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

Limonite (Iron Stone/Goethite)

Limonite (mixture of hydrated iron oxides, primarily Goethite: α-FeO(OH))

Ironstone concretion (possibly limonite/goethite-bearing)

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

Magnetite or Hematite Nodule

Iron Oxide (Fe3O4 or Fe2O3)

Polished dark mineral fragments, likely hematite or magnetite

Hematite (Fe₂O₃) or magnetite (Fe₃O₄)

Hematite

Iron(III) oxide (Fe2O3)

Limonite Concretion

Goethite-rich Concretion (FeO(OH))

Copper Ore Specimen with Malachite

Cuprite, Malachite, and Limonite matrix

Blue metallic mineral specimen, possibly bornite or chalcopyrite

Bornite (Cu₅FeS₄) or chalcopyrite (CuFeS₂); exact identification requires testing