Sedimentary Rock (Specifically A Concretion Or Possibly A Geode)

Geode (Unopened)

Chalcedony Geode (Hydrated Silicon Dioxide, SiO2)

Veined Pebble (likely a Quartz-Veined Pebble)

Pebble with Mineral Vein (e.g., Quartz Vein in a Chert/Mudstone Pebble)

Rounded iron-rich stone or concretion

Indeterminate; possibly hematite-/goethite-bearing sandstone or an ironstone concretion

Quartz Geode

Silicon Dioxide (SiO2)

Agate Geode

Silicon Dioxide (Chalcedony/Quartz), SiO2

Iron-rich weathered stone, possibly limonite/goethite

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

Ironstone Concretion / Goethite Nodules

Ironstone (composed primarily of Goethite FeO(OH) and Limonite)

Ironstone Concretion

Siderite or Ferruginous Concretion (FeCO3 or Iron Oxides)

Yellow quartz-bearing rock, possibly sulfur-stained quartz or calcite

Indeterminate; likely quartz (SiO₂) and/or calcite (CaCO₃) with yellow iron/sulfur staining

Chalcedony Geode Part (Agate/Quartz)

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Likely calcite and quartz-rich specimens

Calcite (CaCO₃), possibly with quartz (SiO₂) or feldspar

Quartz Geode

Silicon Dioxide (SiO2) in Calcareous or Siliceous Matrix

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Siltstone Concretion

Carbonate-cemented Siltstone Concretion

Quartz Geode Fragment

Silicon dioxide (SiO2) within a nodule

Hematite (Concretion)

Iron(III) oxide (Fe2O3)

Quartz Crystal (specifically a Double-Terminated variety)

Silicon Dioxide (SiO2) - Low Quartz

Possible iron-rich pebble or weathered basalt

Indeterminate; likely iron-stained mafic rock, possibly basalt

Quartz Geode

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Amygdaloidal Basalt with Epidote/Chlorite

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

Granite Cobble

Phaneritic Felsic Igneous Rock

Quartz Geode

Silicon Dioxide (SiO2)

Ironstone Concretion / Chert Nodules

Iron-rich Sedimentary Concretion (Fe2O3 / SiO2 mix)

Quartz Geode

Silicon Dioxide (SiO2) within a secondary sedimentary structure

Sandstone (Ferruginous Concretion)

Arenite (with iron oxide cement)

Quartz Geode

Silicon Dioxide (SiO2)

Septarian Nodule (Dragon Stone)

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

Quartz Geode

Silicon Dioxide (SiO2)

Likely weathered quartz-rich rock fragment

Uncertain; possibly quartz sandstone or a pale feldspathic rock

Septarian Nodule (Septarian Dragon Stone)

Septarian Concretion (Composition: Calcite, Aragonite, and Limestone/Clay)

Ironstone concretion

Siderite or Limonite-rich Concretion (FeO(OH)·nH2O)

Sandstone Concretion

Ferruginous Sandstone Concretion (Primarily SiO2 with Iron Oxide cement)

Sandstone Concretion

Ferruginous Sandstone Concretion (SiO2 + FeO(OH))

Ironstone / Hematite Concretion

Iron oxide / Fe2O3

Quartz Geode

Crystalline Silver Oxide (SiO2) in Calcareous Host

Weathered quartz-rich stone, possibly chalcedony or calcite

Likely microcrystalline quartz (SiO₂) or calcite (CaCO₃); exact identification requires testing

Quartz Geode

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Quartz Geode

Crystalline Silicon Dioxide (SiO2)