Sedimentary (Chemically Precipitated)

Sandstone (Ferruginous)

Arenite (primarily SiO2 with Fe2O3 staining)

Banded Chert / Agate

Silicon Dioxide (SiO2)

Veined Limestone

Calcite-veined Limestone (CaCO3)

Druzy Quartz on Limestone

Silicon Dioxide (SiO2) on Calcium Carbonate (CaCO3)

Iron-rich sandstone (Gozan/Ironstone)

Ferruginous Sandstone (clastic sedimentary rock)

Septarian Nodule (Micro-fragment)

Septarian Nodule / Concretion (CaCO3 + CaMg(CO3)2 + Quartz)

Chert / Flint

Microcrystalline Quartz (SiO2)

Banded iron formation (iron-rich metamorphic rock)

Banded iron formation (BIF), chiefly hematite/magnetite with chert or quartz (Fe₂O₃/Fe₃O₄ and SiO₂)

Sandstone with Ironstone Concretion

Arenite with Hematite/Goethite nodules (Fe2O3 / FeO(OH))

Limonite (Iron Ore/Bog Iron)

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

Red Jasper with Quartz Veins

SiO2 (Silicon Dioxide with Iron Oxide inclusions)

Ferruginous Sandstone (Gritstone)

Clastic sedimentary rock with iron-rich cement (FeO(OH)·nH2O)

Quartz / Quartzite

Silicon Dioxide (SiO2)

Weathered iron-rich concretion or ironstone nodule

Goethite–hematite limonite concretion (FeO(OH), Fe₂O₃, and hydrated iron oxides)

Yellow Ocher (Limonite)

Limonite (Hydrated Iron Oxide) - FeO(OH)·nH2O

Orange Calcite

Calcium Carbonate (CaCO3)

Sulfur-bearing Limestone (Solfatara Specimen)

Sulfur-rich Bio-limestone (Calcium Carbonate with Native Sulfur, S8)

Ferruginous Sandstone

Arenite with Hematite/Goethite cement

Moqui Marble (Ironstone Concretion)

Goethite/Hematite Concretion (Fe2O3 / FeO(OH))

Ferruginous Sandstone

Arenite with Iron-oxide cement (composed of Quartz and Limonite/Hematite)

Fossilized Limestone with Crinoid Stem

Carboniferous Limestone (containing Crinoidea ossicles)

Yellow Calcite (Banded)

Calcium Carbonate (CaCO3)

Orange Calcite

Calcium Carbonate (CaCO3)

Banded Chert / Flint

Silicon dioxide (SiO2)

Limestone

Calcium Carbonate (CaCO3)

Ferruginous Sandstone (Ironstone Nodules)

Ferruginous Sandstone with Limonite/Goethite coating (Fe2O3·H2O)

Blue-green calcite

Calcite (CaCO₃), likely copper-bearing or otherwise inclusions-colored

Limonite

FeO(OH)·nH2O

Limestone

Calcium Carbonate (CaCO3)

Banded Iron Formation (Fragment)

Banded Iron Formation (BIF)

Weathered iron-rich concretion (probable limonite/goethite)

Limonite–goethite aggregate, approximately FeO(OH)·nH₂O

Sandstone (Ferruginous)

Arenite (iron-rich)

Sandstone (Ferruginous)

Arenite (composed primarily of SiO2 with Fe2O3 cement)

Likely weathered limestone or calcite-rich stone

Limestone, primarily calcium carbonate (CaCO₃), possibly calcite

Banded Iron Formation

Banded Iron Formation (BIF)

Lake Superior Agate

Silicon Dioxide (SiO2) - variety: banded chalcedony quartzite

Limestone

Calcium Carbonate (CaCO3)

Dendritic Siltstone (or Mudstone)

Siltstone with Manganese Oxide dendrites

Septarian Nodule Segment (Commonly known as Dragon Stone or Lightning Stone)

Septarian Nodule (CaCO3 / Hydrated Calcium Carbonate)

Ferruginous Sandstone (Gritstone)

Arenite with Iron-Oxide Cement (SiO2 with Fe2O3 and FeO(OH))

Septarian Nodule (Thunder Egg variant)

Septarian concretion (Calcite, Aragonite, and Limestone)

Psilomelane (Black Hematite/Manganese Ore)

Barium Manganese Oxide (Formula: BaMn9O18(OH)4)