Organic Structure (Not A Rock)

Dyed Purple Agate

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

Eclogite

Eclogite (Omphacite + Almandine-Pyrope Garnet)

Fossiliferous Limestone (Coquina / Shell Conglomerate)

Bioclastic Limestone (composed primarily of CaCO3)

Fossilized Brachiopod/Bivalve in Limestone

Brachiopoda or Bivalvia fossil in Calcite/Limestone (CaCO3)

Granite

Phaneritic intrusive igneous rock (composition: Quartz, Alkali Feldspar, Plagioclase Feldspar)

Coquina

Bioclastic Limestone

Vesicular Basalt with Lichen

Vesicular Basalt

Vesicular Basalt (River Rock)

Afanitic Vesicular Basalt

Granite

Intrusive Igneous Rock (composed of Quartz, Alkali Feldspar, and Plagioclase)

Sandstone (Quartz-rich)

Arenite (primarily SiO2)

Sandstone (Ferruginous)

Clastic Sedimentary Rock (SiO2 with FeO/Fe2O3)

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Basalt

Basalt (Mafic volcanic rock)

Oolitic Limestone

Oolitic Carbonate (CaCO3)

Quartz vein in Host Rock

Crystalline Silicon Dioxide (SiO2) in Lithic Matrix

Druzy Quartz (on Quartzite or Chert)

Silicon Dioxide (SiO2)

Turquoise in Matrix

Hydrated phosphate of copper and aluminum (CuAl6(PO4)4(OH)8·4H2O)

Quartz in Matrix (possibly with Biotite or Hornblende)

Quartz (Silicon Dioxide, SiO2) in Granitic Matrix

Limestone

Calcium Carbonate (CaCO3)

Quartz Druzy on Basalt

Silicon Dioxide (SiO2) on Mafic Volcanic Rock

Granite

Granite (a common type of Felsic Intrusive Igneous Rock)

Quartzite

Quartzite (SiO2)

Anthracite Coal

Anthracite (Carbon-rich metamorphic coal)

Quartz Pebble

Silicon Dioxide (SiO2)

Granite

Granite (a common igneous rock)

Thunderegg (Ate Agate/Jasper Geode)

Silicon Dioxide (SiO2) within Rhyolite/Perlite matrix

Mahogany Obsidian

Obsidian (Volcanic Glass) with Hematite/Magnetite inclusions

Tiger's Eye

Pseudomorph of Quartz after Crocidolite (SiO2 with iron oxide inclusions)

Septarian Nodule (Dragon Stone)

Septarian Nodule (Calcium Carbonate/Aragonite/Calcite Concretion)

Chert (specifically a stream-worn Chert Nodule)

Sedimentary Cryptocrystalline Quartz (SiO2)

Agate Geode

Silicon Dioxide (SiO2) - variety Chalcedony/Quartz

Pearl

Calcium Carbonate (CaCO3) - Aragonite/Calcite organic gemstone

Basalt Pebble

Basalt

Quartzite (Water-worn Cobble)

Quartzite (Composition: 90%+ SiO2)

Quartz Druze on Matrix

Silicon Dioxide (SiO2)

Blue Dyed Agate Geode

Chalcedony (cryptocrystalline Quartz), SiO2

Sandstone (lithic/greywacke variant)

Clastic sedimentary rock (primarily SiO2 with rock fragments)

Basalt

Basalt (Extrusive Mafic Igneous)

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Amphibolite with Hornblende

Amphibole-rich Metamorphic Rock (Ca2(Mg,Fe)5Si8O22(OH)2)

Picture Jasper

Silicon Dioxide (SiO2) with iron oxide and organic impurities

Basalt

Basalt (Mafic Extrusive)