Sedimentary Rock (Specifically A Concretion Or Possibly A Geode)

Concretion with Geode Cavity

Ferruginous Sandstone Concretion with Quartz Center

Ironstone Concretion (Coprolite-like)

Goethite/Hematite Siderite Spheroid (FeCO3 or FeO(OH))

Shale with Coprolite influence

Argillaceous sedimentary rock (Shale/Mudstone)

Limonite Geode (Ironstone Concretion)

FeO(OH)·nH2O (Hydrated Iron Oxide)

Quartz Geode

Silicon Dioxide (SiO2) in a concretion

Pebble

Clast (specifically a granule or small pebble)

Limonite Geode / Ironstone Concretion

Hydrated iron oxide-hydroxide (FeO(OH)·n H2O)

Concretion

Sedimentary Concretion

Sandstone Concretion with Quartz Center

Sedimentary Clastic Rock (SiO2 matrix with Quartz core)

Quartz geode with drusy quartz crystals

Quartz, silicon dioxide (SiO₂), commonly colorless to milky crystalline quartz

Likely polished/tumbled fossil shell or concretion

Indeterminate; possibly a fossil bivalve or gastropod in mineralized matrix

Weathered carbonate rock, possibly fossiliferous limestone

Calcite-rich limestone (CaCO₃), tentative identification

Ironstone Concretion (Moqui Marble)

Iron-oxide Concretion (Hydrated ferric oxide, Fe2O3·nH2O)

Sandstone Concretion

Sedimentary concretion

Ironstone Concretion / Goethite-Hematite Geode

Goethite / Hematite Concretion (Fe3O4 / FeO(OH) / Fe2O3)

Septarian Nodule

Septarian Concretion (Complex of Calcite, Aragonite, and Limestone/Mudstone)

Agate Geode

Banded Chalcedony (Silicon Dioxide, SiO2) with Quartz crystals

Concretion

Sedimentary Concretion (Ironstone / Calcite Concretion)

Septarian Nodule (Dragon Stone)

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

Concretion

Various mineral compositions, typically carbonate or iron oxide cemented sediment

Rounded river pebble, likely fine-grained sandstone or siltstone

Indeterminate clastic sedimentary rock; possibly quartz-rich sandstone

Geode (Unopened)

Silica Concretion / Geode (Formula: SiO2 for quartz internal contents)

Quartz Geode

Silicon Dioxide (SiO2)

Quartz Crystal

Silicon Dioxide (SiO2)

Dark mineral nodule with white veining

Possibly a calcite-veined manganese- or iron-rich concretion; exact identification requires testing

Clear Quartz (Druzy)

Crystalline Silicon Dioxide (SiO2)

Chalcedony Geode Fragment (Botryoidal)

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

Quartz Druzy

Silicon Dioxide (SiO2)

Quartz Geode (likely within Limestone or Dolomite matrix)

Quartz (SiO₂)

Weathered iron-rich concretion or breccia

Goethite/hematite-bearing limonite concretion, possibly ferruginous sandstone

Geode

Quartz nodule / Chalcedony-lined cavity

Weathered iron-rich stone, possibly limonite-bearing sandstone or laterite

Goethite–hematite/limonite mixture; exact identification requires testing

Quartz (Druzy Quartz)

Silicon Dioxide (SiO2)

Limonite Geode / Ironstone Concretion

Hydrated Iron Oxide (FeO(OH)·nH2O)

Quartz-lined geode

Silica geode; predominantly microcrystalline quartz (SiO₂), possibly chalcedony

Quartz Geode

Silicon Dioxide (SiO2)

Weathered iron-rich stone, possibly sandstone or ironstone

Indeterminate; likely quartz-rich sandstone with iron-oxide cement, possibly hematite/goethite

Weathered iron-rich stone, possibly limonite-bearing sandstone or laterite

Limonite/goethite-rich material; composition commonly FeO(OH)·nH₂O with clay and quartz impurities

Iron-rich concretion or slag-like rock

Goethite–hematite limonite concretion, possibly iron slag

Amethyst (Rough)

Silicon Dioxide with iron impurities (SiO2)

Small white mineral fragment

Likely quartz (SiO₂), possibly calcite (CaCO₃)

Concretion

Sedimentary Concretion (e.g., Siderite or Ironstone)