Sedimentary Rock (Specifically A Concretion Or Possibly A Geode)

Ironstone Concretion (Limonite/Goethite)

Goethite/Limonite concretion (FeO(OH)·nH2O)

Ironstone Concretion (Moqui Marble type)

Iron oxide concretion (Goethite/Hematite and Sandstone)

Dark gray metamorphic cobble, likely slate or phyllite

Foliated metapelite; possibly slate/phyllite composed mainly of quartz, mica, and chlorite

Likely weathered iron-rich concretion or jasper

Goethite/hematite-bearing chert or ferruginous concretion (identification uncertain from photograph)

Quartz Geode

Silicon Dioxide (SiO2)

Ironstone Concretion (likely)

Goethite/Hematite/Limonite cemented sediment

Chert Concretion / Nodule

Microcrystalline Quartz (SiO2)

Sandstone (with potential Concretion or Fossil fragment)

Arenite (primarily SiO2)

Unopened Geode

Geode (containing various mineralization like Quartz SiO2)

Geode (Unopened)

Quartz Geode (SiO2-rich chalcedony/quartz nodule)

Agate Geode

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Quartz Geode

Crystalline Silicon Dioxide (SiO2) in Geode

Bumblebee Jasper

Fibrous Calcite and Quartz with Volcanic Matter (CaCO3 / SiO2)

Probable fossil-bearing rock or mineral concretion

Unidentified carbonate-rich concretion with a possible fossil inclusion

Conglomerate (polymictic, possibly metamorphosed)

Polymictic conglomerate; clasts cemented in a dark, likely quartz-rich matrix

Chalcedony Geode / Quartz Druzy

Silicon Dioxide (SiO2)

Ironstone / limonitic iron-rich rock

Goethite–hematite–limonite aggregate, commonly an ironstone concretion

Polished Agate (Green and White Chalcedony)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Quartz Druzy (on Matrix)

Silicon Dioxide (SiO2)

Gneiss (specifically a granitic gneiss cobble)

Gneiss (high-grade regional metamorphic rock)

Generic Pebble

Lithic Fragment

Shale

Lutaceous Rock (Hydrous Aluminum Silicates)

Quartz

Quartz (SiO2 - Silicon Dioxide)

Basalt with Quartz/Calcite Veins

Amygdaloidal Basalt (SiO2 or CaCO3 inclusions)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Weathered light-colored rock, possibly quartz-rich granite or quartzite

Indeterminate; likely quartz–feldspar rock (granite) or quartzite

Jasper (specifically Bloodstone/Heliotrope or Dark Green Jasper)

Cryptocrystalline Quartz (SiO2) with inclusions

Sandstone (Ferruginous)

Arenite with Iron Oxide staining (Fe2O3)

Quartz cluster, possibly druzy quartz on matrix

Quartz (SiO₂), likely microcrystalline to coarse crystalline; associated matrix uncertain

Sandstone

Arenite (specifically Quartz Arenite)

Quartz Geode (Cracked)

Crystalline Silicon Dioxide (SiO2)

Weathered iron-rich concretion or ironstone cobble

Limonite/goethite-rich ironstone, commonly with hematite and quartz

Vesicular Basalt (Scoria)

Mafic extrusive igneous rock (primarily Plagioclase Feldspar and Pyroxene)

Ironstone concretion

Iron-oxide-cemented sedimentary concretion, commonly composed of goethite and/or hematite with quartz or clay

Red Jasper (possibly banded)

Silicon Dioxide (SiO2) with iron oxide inclusions

Smoky Quartz

Silicon Dioxide (SiO2)

Amethyst Geode

Silicon dioxide (SiO2) with iron impurities

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Sandstone with Brachiopod Mold Fossil

Sedimentary rock (Sandstone) with indeterminate Brachiopod mold

River Cobble (Basaltic/Andesitic)

Mafic Igneous Porphyritic Rock

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Concretion

Septarian Concretion