Sedimentary Rock (Specifically A Concretion Or Possibly A Geode)

Quartz Geode

Silicon Dioxide (SiO2)

Septarian Nodule (Yellow Jasper variety)

Septarian Nodule (comprising Calcite, Aragonite, and Limestone/Bentonite)

Quartz Geode

Silicon Dioxide (SiO2)

Geode Nodules / Chalcedony Geode

Silicon Dioxide (SiO2) - Amorphous to Cryptocrystalline Quartz

Chert Nodules or Concretion

Cryptocrystalline Quartz (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Likely water-worn gray pebble

Not identifiable to a specific rock from this image; possibly fine-grained basalt or another dark river-worn rock

Concretion (likely iron-rich sandstone or claystone concretion)

Diagenetic carbonate/iron-oxide concretion; exact mineralogy requires testing

Quartz Geode

Quartz (Silicon Dioxide - SiO2) within a Chalcedony and Limonite shell

Ironstone Concretion (Iron Nodule)

Hydrated Iron Oxide Concretion (predominantly Goethite, Α-FeO(OH), and Hematite, Fe2O3)

Druzy Quartz Geode (Oco or Moroccan variety)

Silicon Dioxide (SiO2)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Quartz geode

Microcrystalline quartz (chalcedony) lining a cavity with crystalline SiO₂ quartz

Amethyst-bearing quartz

Quartz, SiO₂; purple variety colored mainly by iron-related defects

Crescent Pebble

Weathered Quartzite or Sandstone Fragment

Ironstone Concretion (Moqui Marble / Boji Stone)

Sedimentary Iron Oxide Concretion (Fe2O3 / FeO(OH))

Fossiliferous limestone concretion

Calcite-rich limestone (primarily CaCO₃), possibly containing a fossil shell or coral fragment

Quartz-rich feldspathic rock, possibly granite or arkose

Granite-like aggregate of quartz (SiO₂), feldspar, and minor iron oxides

Septarian Nodule or Concretion

Calcareous concretion with argillaceous and sideritic components

Weathered limestone or concrete-like calcareous rock

Limestone; predominantly calcite (CaCO₃), possibly containing dolomite and silicate impurities

White limestone, possibly chalky limestone

Calcite-rich carbonate rock; predominantly calcium carbonate (CaCO₃)

Weathered limestone or calcareous concretion

Predominantly calcite (CaCO₃), possibly a fossil-rich limestone fragment

Ironstone Concretion (Limonite/Goethite)

Goethite-rich Concretion (FeO(OH))

Omarolluk

Omarolluk (Siliceous greywacke with hemispherical voids)

Quartz Geode

Silicon Dioxide (SiO2)

Geode (Chert or Quartz Nodule)

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2) in sedimentary host rock

Quartz-bearing geode or vuggy quartz specimen

Quartz, silicon dioxide (SiO₂), possibly with chalcedony and iron-oxide staining

Vesicular Basalt (Scoria)

Extrusive Mafic Igneous Rock (primarily Plagioclase Feldspar and Pyroxene)

Quartz Geode

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Gneiss (specifically Biotite Gneiss)

Gneiss (high-grade metamorphic rock primarily composed of Silicates)

Amethyst crystal cluster

Amethyst, purple variety of quartz (SiO₂)

Geode with Quartz/Chalcedony

Silicon Dioxide (SiO2)

Gabbro

Gabbro (mafic intrusive igneous rock)

Leopard Skin Jasper

Orbicular Jasper (Silicon Dioxide, SiO2)

Ironstone Concretion (Moqui Marble type)

Ironstone Concretion (Fe2O3 with SiO2 core)

Dragon Vein Agate

Silicon Dioxide (SiO2)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Geode (Unopened)

Silicon Dioxide (SiO2) in sedimentary vugs

Quartz Geode / Druzy Quartz

Silicon Dioxide (SiO2)

Chert (Agatized/Chalcedony variety)

Microcrystalline Quartz (SiO2)