Sedimentary Rock (Specifically A Concretion Or Possibly A Geode)

Sandstone Concretion

Sedimentary Concretion (Quartz sand bound by mineral cement)

Geode

Crystalline Quartz in Sedimentary Matrix (SiO2)

Vesicular Basalt (or Scoria)

Extrusive Igneous Rock (Mafic)

Concretion

Septarian Concretion (Clay-Ironstone Nodules)

Limonite Concretion

FeO(OH)·nH2O (Hydrated Iron Oxide)

Cannonball Concretion

Calcite-cemented Sandstone Concretion

Basalt

Basalt (composition of plagioclase feldspar and pyroxene)

Weathered iron-rich concretion or limonite/goethite nodule

Limonite (largely hydrated iron oxides; commonly goethite, FeO(OH), and hematite, Fe₂O₃)

Quartz Geode

Silicon Dioxide (SiO2) in Geodic habit

Ironstone concretion (possibly limonite/goethite-bearing)

Limonite, a mixture of hydrated iron oxides, commonly including goethite (α-FeO(OH))

Ironstone concretion (possibly pyrite-bearing)

Iron-rich sedimentary concretion, likely composed of goethite/limonite with possible pyrite

Sandstone concretion

Arenite sedimentary rock (concretion/nodule)

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Blue Celestine

Celestine (SrSO4)

Claystone Concretion

Septarian Concretion (Ironstone-rich)

Quartz Geode

Silicon Dioxide (SiO2)

Geode (Unopened)

Siliceous Geode (SiO2)

Sandstone Concretion

Sedimentary Concretion (Quartz sandstone with iron oxide cement)

Quartz Geode

Silicon Dioxide (SiO2) within a geode

Thunderegg (specifically a Jasper/Agate-filled Geode nodule)

Silicon Dioxide (SiO2) within Rhyolitic Matrix

Concretion

Septarian or Siderite Concretion

Likely weathered iron-rich stone or concretion

Indeterminate; possibly ferruginous sandstone, ironstone, or a weathered sedimentary concretion

Dyed Blue Agate

Silicon dioxide (SiO2) with artificial pigment

Jasper (or possibly Agate/Chalcedony) beads

SiO2 (Silicon Dioxide)

Possible fossilized ammonite or concretion

Indeterminate fossil specimen; possibly an ammonoid mold/cast in iron-rich sedimentary rock

Agate Geode

Silicon Dioxide (SiO2) - Chalcedony variety

Iron-rich rock, possibly limonite/goethite-bearing quartz or weathered ironstone

Limonite (FeO(OH)·nH₂O), commonly mixed with goethite (α-FeO(OH)) and quartz

Quartz Geode

Quartz (Silicon Dioxide, SiO2)

Geode (Quartz / Chalcedony Geode)

SiO2 (Silicon Dioxide)

Agate Geode

Silicon Dioxide (SiO2) - Chalcedony variety

Likely iron-rich concretion or weathered rock pebble

Uncertain from the image; possibly an iron-oxide-cemented concretion (goethite/hematite)

Sandstone Concretion

Septarian Concretion (Nodule)

Sandstone (with Concretion)

Arenite / Quartzose Sandstone

Chert (or possibly Flint)

SiO2 (Silicon Dioxide)

Quartz Geode

Silicon Dioxide (SiO2)

Quartz geode

Quartz (SiO₂), likely a chalcedony-lined geode with drusy quartz crystals

Chalcedony geode or quartz-rich agate nodule

Microcrystalline quartz, SiO₂, with possible crystalline quartz druse

Quartz geode nodule (possibly chalcedony)

Silica, SiO₂; quartz or microcrystalline quartz (chalcedony)

Moqui Marble

Iron Oxide Concretion (Fe2O3 / FeO(OH))

Iron-rich rock, possibly limonite/goethite

Hydrated iron oxides/hydroxides, commonly limonite (FeO(OH)·nH₂O) with goethite (α-FeO(OH))

Moqui Marble (Shaman Stone)

Ironstone Concretion (Iron oxide Fe2O3 and FeO(OH))

Sandstone (likely Graywacke or Siltstone variety)

Clastic Sedimentary Rock (SiO2 with assorted mineral fragments)