Sedimentary Rock (Specifically A Concretion Or Possibly A Geode)

Limonite Concretion

Goethite-rich Concretion (FeO(OH))

Sandstone

Arenite (primarily SiO2)

Druzy Quartz Geode (likely Smokey Quartz variety)

Silicon Dioxide (SiO2) - specifically a geode formation lined with druzy quartz crystals, with a likely brownish hue indicating smokey quartz.

Gneiss (specifically a weathered Amphibolite or Garnet Gneiss)

Gneiss (complex silicate composition)

Limestone (specifically Dolomitic Limestone)

Calcium Magnesium Carbonate (CaMg(CO3)2)

Ironstone Concretion

Siderite or Ferruginous Concretion (FeCO3 or Iron Oxides)

Quartz Geode

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Septarian Nodule (Dragon Stone)

Septarian concretion (Complex of Calcite, Aragonite, and Limestone/Clay)

Sandstone with Iron Concretion

Arenite with Limonite/Goethite Concretion

Banded Agate (specifically Carnelian Agate slice)

Chalcedony (cryptocrystalline variety of Quartz), SiO2

Amethyst (Geode/Druzy)

Silicon Dioxide (SiO2) with iron impurities

Unidentifiable Specimen

Undetermined

Chert / Flint Nodules in Sandstone

Microcrystalline Quartz (SiO2) within Clastic Sedimentary Rock

Iron Ore / Ironstone Concretion

Mixture of iron oxide/hydroxide minerals, likely some combination of Hematite (Fe2O3), Goethite (α-FeOOH), and Limonite (a general term for hydrated iron oxides of variable composition) or potentially Bauxite (a mixture of aluminum hydroxides, often with iron oxides, (Al(OH)3) and FeO(OH)). The visual characteristics strongly suggest iron-rich material.

Quartz Geode

Silicon Dioxide (SiO2)

Geode Nodules / Chalcedony Geode

Silicon Dioxide (SiO2) - Amorphous to Cryptocrystalline Quartz

Quartz Geode

Silicon Dioxide (SiO2)

Sandstone Concretion

Ferruginous Sandstone Concretion (Primarily SiO2 with Iron Oxide cement)

Quartz (Druzy or Geode fragment)

Silicon Dioxide (SiO2)

Sandstone Concretion

Septarian or Carbonate-cemented Sandstone Concretion

Druzy Quartz Geode (Oco or Moroccan variety)

Silicon Dioxide (SiO2)

Blue Celestite (Celestine)

Strontium sulfate (SrSO4)

Painted Garden Rock (likely Granite or Limestone base)

Silicon Dioxide (SiO2) / Calcium Carbonate (CaCO3) based substrate with Acrylic/Enamel pigments

Amygdaloidal Basalt with Epidote/Chlorite

Basalt (containing (Ca2(Al2Fe3+)(SiO4)(Si2O7)O(OH)))

Sandstone Concretion

Clastic sedimentary rock (primarily Silica, SiO2, or Calcium Carbonate, CaCO3)

Geode (unopened)

Calcedony-lined Geode (SiO2)

Sandstone Concretion

Moqui Marble / Iron-oxide Concretion (SiO2 with Hematite/Goethite)

Unidentifiable Rock Fragment

Sandstone Geode (Unbroken)

Siliciclastic sedimentary rock (primarily Quartz)

Geode (Unopened)

Silicon Dioxide (SiO2) in sedimentary vugs

Siltstone/Sandstone (possibly Wonderstone or Picture Sandstone)

Clastic Sedimentary Rock (primarily SiO2 with Iron Oxide inclusions)

Concretion with Quartz Veining

Septarian Concretion (CaCO3 / SiO2)

Quartz on Sandstone

Silicon Dioxide (SiO2) in Lithic Sandstone

Basalt

Basalt (composition: Plagioclase, Pyroxene, and Olivine)

Sandstone (specifically Cross-bedded Sandstone)

Arenite (composed primarily of SiO2)

Shale with Vein Infillings

Shale (a fine-grained clastic sedimentary rock). The veins could be Calcite (CaCO3), Quartz (SiO2), or other minerals.

Quartz Crystal (specifically a Double-Terminated variety)

Silicon Dioxide (SiO2) - Low Quartz

Man-made Synthetic Material (Plastic/Composite)

Acrylonitrile Butadiene Styrene (ABS) or High-Impact Polystyrene (HIPS)

Quartz Geode

Crystalline Silicon Dioxide (SiO2) in Geode form

Geode with Quartz/Chalcedony

Silicon Dioxide (SiO2)

Chert Geode or Nodule

Microcrystalline Quartz (SiO2)