Sedimentary Rock (Specifically A Concretion Or Possibly A Geode)

Limonite Concretion

Limonite (Hydrated Iron Oxide) FeO(OH)·nH2O

Limestone Concretion (Botryoidal/Calcareous Nodules)

Calcium Carbonate Concretion (CaCO3)

Quartz Geode

Silicon Dioxide (SiO2)

Polymictic breccia, possibly volcanic breccia

Polymictic clastic breccia; likely a matrix-supported breccia containing lithic fragments, quartz, feldspar, and dark mafic minerals

River Rocks and Pebbles

Mixed Silica-rich Sediments (SiO2 based)

Quartz Geode Fragment

Silicon dioxide (SiO2) within a nodule

Ironstone Concretion

Ferruginous Sandstone / Iron-rich Sedimentary Rock

Quartz Geode

Silicon Dioxide (SiO2)

Pebble (likely a type of sandstone or quartzite pebble)

Clastic Sediment (specifically, a rudite-sized clast). If the pebble is composed of a specific rock type, its scientific name would be that rock type (e.g., 'Quartzite pebble', 'Granite pebble', 'Chert pebble'). Given its appearance, it is likely a metamorphic quartzite pebble or a hard sandstone pebble.

Quartz Geode

Silicon Dioxide (SiO2)

Limestone (specifically Dolomitic Limestone)

Calcium Magnesium Carbonate (CaMg(CO3)2)

Hematite Concretion

Iron oxide (Fe2O3) in concretionary form

Sandstone Concretion

Sandstone (Sedimentary Rock) with silica or calcite cement

Gneiss (specifically a weathered Amphibolite or Garnet Gneiss)

Gneiss (complex silicate composition)

Agate (specifically Chalcedony/Banded Agate)

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Limitation Concretion

Ironstone Concretion (Goethite/Limonite)

Quartz Geode

Silicon Dioxide (SiO2) within a secondary sedimentary structure

Quartz Geode

Silicon Dioxide (SiO2)

Chert (specifically a Worked Flint/Knapped Flake)

Chert / Flint (Microcrystalline Quartz, SiO2)

Quartz geode with iron-oxide matrix

Quartz (SiO₂), likely with limonite/goethite and possibly calcite

Ironstone Concretion

Ironstone (Siderite/Goethite/Hematite matrix)

Geode (Unopened)

Silicon Dioxide (SiO2) in sedimentary host rock

Chert Concretion

Chert (Microcrystalline Quartz, SiO2)

Ironstone Concretion (Ironstone Gourd)

Limonite/Goethite Concretion (FeOO(H))

Limonite Concretion

Goethite-Limonite (FeO(OH)·nH2O)

Sandstone Concretion

Clastic Sedimentary Rock (primarily SiO2 with mineral cement)

Dalmatian Stone

Aplite (often incorrectly called Dalmatian Jasper)

Quartz Geode

Silicon Dioxide (SiO2)

Sandstone Concretion

Carbonate-cemented Sandstone Concretion

Quartz Geode

Silicon Dioxide (SiO2) in Geode formation

Quartz Geode

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Basalt

Aphanitic Mafic Igneous Rock

Sandstone Geode

Sedimentary Geode (Silica/Calcite composition)

Quartz Geode in Sedimentary Host Rock

Silicon Dioxide (SiO2) in Carbonate Matrix

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Crescent Pebble

Weathered Quartzite or Sandstone Fragment

Limonite Concretion

Goethite-rich Concretion (FeO(OH))

Quartz Geode

Silicon Dioxide (SiO2) in Geodic Cavity

Red Jasper (possibly banded)

Silicon Dioxide (SiO2) with iron oxide inclusions

Quartz Geode Fragment

Silicon Dioxide (SiO2)