Sedimentary (Chemically Precipitated) Or Metamorphic

Agate (specifically Lace Agate or Banded Agate)

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Hematite (Iron Ore)

Hematite (Fe2O3)

Red Quartzite / River Cobble

Quartzite (SiO2 with iron oxide impurities)

Quartzite

Quartzite (SiO2)

Tiger's Eye (Rough)

Pseudomorph of Quartz after Crocidolite (SiO2 with Iron inclusions)

Zircon

Zirconium Silicate (ZrSiO₄)

Banded Agate

Cryptocrystalline Quartz (SiO2)

Orange Calcite

Calcium Carbonate (CaCO3)

Blue Quartz (Aventurine)

Silicon Dioxide (SiO2) with inclusions of Dumortierite or Magnesio-riebeckite

Iceland Spar (Optical Calcite)

Calcite (Calcium Carbonate, CaCO3)

Limonite (Ochreous)

FeO(OH)·nH2O (Hydrated Iron Oxide)

Chert (and Jasper/Chalcedony mixture)

Microcrystalline Quartz (SiO2)

Goethite (likely as part of Limonite/Ironstone)

Goethite (α-FeOOH)

Quartzite (with possible Calcite/Limestone weathering)

Quartzite (primarily SiO2)

Quartz (River Cobble)

Silicon Dioxide (SiO2)

Limestone (specifically Fossiliferous or Crinoidal Limestone)

Calcium Carbonate (CaCO3) - Calcite Rock

Septarian Nodule (Dragon Stone)

Septarian concretion (composition: Calcium Carbonate / Calcite, Aragonite, and Limestone/Clay)

Limonite with Trace Fossils

Hydrous Iron Oxide Mixture (FeO(OH)·nH2O)

Bauxite

Bauxite (mixture of Hydrous Aluminum Oxides)

Bauxite

Bauxite (Al(OH)3, γ-AlO(OH), and α-AlO(OH))

Bauxite

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

Quartzite

Quartzite (primarily SiO2)

Ferruginous Sandstone (Grit)

Clastic Sedimentary (Ironstone-rich Sandstone)

Jasper Geode

Silicon Dioxide (SiO2) with impurities

Agate (translucent pebble)

Silicon dioxide (SiO2) - Microcrystalline Quartz

Jasper with Quartz Vein

Silicon Dioxide (SiO2) with impurities

Septarian Nodule (or Mudstone with Septarian Cracking)

Septarian Concretion (Composition: Calcite, Aragonite, and Limestone/Claystone)

Sandstone (likely River-tumbled Picture Sandstone)

Arenite (predominantly SiO2 with iron oxide impurities)

Moqui Marble

Iron Oxide Concretion (Limonite/Hematite over Sandstone)

Jasper

Jasper (Silicon Dioxide, SiO2)

Oolite or Oolitic Limestone

Oolitic Limestone (Principal mineral: Calcite, CaCO3)

Ferruginous Sandstone (Ironstone)

Ferruginous Sandstone / Limonite-cemented Quartz Sandstone

Kyanite

Kyanite (Al2SiO5)

Travertine (often colloquially called Tufa)

Chemical Sedimentary Calcium Carbonate (CaCO3)

Diabase (Dolerite)

Mafic Intrusive Igneous Rock

Red Garnet (Almandine-Pyrope series)

Garnet Group, Almandine (Fe3Al2(SiO4)3) or Pyrope (Mg3Al2(SiO4)3)

Garnet (likely Almandine or a blend)

Garnet group: X3Y2(SiO4)3, where X can be Ca, Mg, Fe2+, Mn2+ and Y can be Al, Fe3+, Cr3+. Given the dark, somewhat reddish-brown appearance in the image, it's likely Almandine (Fe3Al2(SiO4)3) or a mix with other iron-rich garnets.

Quartzite (River Cobble)

Quartzite (SiO2)

Quartzite with Dark Mineral Inclusions

Quartzite (primarily SiO2) with accessory minerals

Tiger's Eye

Pseudomorph of Quartz after Crocidolite (SiO2 with inclusions of Iron Oxide)

Quartzite

Quartzite (Primary mineral: SiO2)