Sedimentary

Chert (Flint)

Chert (SiO2)

Conglomerate

Conglomerate (SiO2 dominant in clasts)

Limonite (often after Pyrite)

Limonite (FeO(OH)·nH2O)

Petrified Wood (Silicified Wood)

Silicified Paleoflora (mainly Quartz, SiO2)

Sandstone (Ferruginous)

Ferruginous Sandstone (SiO2 with Fe2O3)

Milky Quartz Geode or Druzy Quartz

Silicon Dioxide (SiO2)

Limonite (Iron Ore)

Hydrous ferric oxides (FeO(OH)·nH2O)

Limonite Geode (Ironstone Concretion)

FeO(OH)·nH2O (Hydrated Iron Oxide)

Chert Nodules (Limonitic Chert)

Cryptocrystalline Quartz (SiO2) with Hydrated Iron Oxides

Limestone

Limestone (Calcium Carbonate, CaCO3)

Chert (Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Siltstone

Siltstone (primarily composed of quartz and clay minerals)

Chert (Flint)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Fossilized Gastropod Internal Mold

Steinkern (Mollusca: Gastropoda)

Banded Chert with Quartz Veining

Microcrystalline Quartz (SiO2)

Glauconitic Sandstone

Glauconitic Quartz Arenite

Fossiliferous Limestone

Fossiliferous Limestone (CaCO3)

Chert (and Limestone)

Silicon Dioxide (SiO2)

Sandstone (with Iron Staining)

Arenite (SiO2 predominantly)

Petrified Wood

Silicified Wood (primarily Quartz/Chalcedony, formula SiO2)

Quartz on Matrix

Silicon Dioxide (SiO2)

Chert (Iron-stained)

Chert (primarily Microcrystalline Quartz, SiO2)

Opal

Hydrated amorphous silica (SiO2·nH2O)

Chert (Jasper/Limonitic Chert)

Silicon dioxide (SiO2)

Vesicular Basalt or Hag Stone

Basalt (with vesicles) or bored Sedimentary Rock

Calcite on Limestone

Calcium Carbonate (CaCO3) on Sedimentary Rock

Sandstone

Arenite (primarily SiO2)

Sandstone with Quartz Veining

Arenite with SiO2 veins

Sandstone (Ferruginous)

Arenite with Iron Oxide staining (Fe2O3)

Sandstone (Quartzose)

Arenite (Formula: SiO2 primary, with various cements)

Sandstone (Ferruginous)

Arenite with Iron Oxides

Chert / Jasper

Microcrystalline Quartz (SiO2)

Sandstone

Arenite (primarily SiO2)

Limestone

Calcium Carbonate (CaCO3)

Sandstone (River Rock)

Arenite (composed primarily of SiO2)

Limestone (River Stone)

Calcium Carbonate (CaCO3)

Sandstone (Flagstone)

Arenite (composed primarily of SiO2)

Limestone

Calcium Carbonate (CaCO3)

Sandstone (Ferruginous)

Arenite (composed primarily of SiO2 with Fe2O3 staining)

Sandstone with Calcite Vein

Clastic sedimentary rock (primarily SiO2) with Calcium Carbonate (CaCO3) infilling

Bauxite

Bauxite (mixture including Gibbsite Al(OH)3, Boehmite γ-AlO(OH), and Diaspore α-AlO(OH))

Sandstone

Arenite (composed primarily of Quartz: SiO2)