Rock (Likely Sedimentary)

Sandstone

Arenite (primarily SiO2)

Weathered sandstone or iron-stained limestone fragment

Likely quartz-rich sandstone (SiO₂) or calcitic limestone (CaCO₃); exact identification requires testing

Fossiliferous Limestone

Calcareous Sedimentary Rock (CaCO3)

Chert (Iron-rich River Pebble)

Cryptocrystalline Quartz (SiO2)

Sandstone Cobble with Iron Staining

Arenite with Limonite/Goethite coatings

Sandstone (with Iron Staining)

Clastic sedimentary rock (primarily SiO2 with Fe2O3 oxides)

Sandstone (Quartzose Sandstone)

Clastic Sedimentary Rock (Lithic arenite / Quartz arenite)

Sandstone (with biological crust)

Arenite (SiO2 based)

Weathered chert or siliceous limestone

Microcrystalline quartz (SiO₂), possibly with carbonate minerals

River Pebble (Gravel)

Clastic sedimentary rock (likely Siltstone or Mudstone pebble; SiO2 with various impurities)

Likely biotite-bearing metamorphic rock (schist or gneiss)

Mica schist/gneiss; chiefly quartz, feldspar, and biotite mica

Likely weathered sandstone or iron-stained quartzite fragment

Quartz-rich sandstone (predominantly SiO₂; exact identification uncertain from image)

Weathered quartz-rich rock, likely sandstone or quartzite

Quartz arenite (sandstone) or quartzite; predominantly SiO₂

Calcite on Limestone

Calcium Carbonate (CaCO3) on Sedimentary Rock

Chert (or Chalcedony) Nodule

Microcrystalline Quartz (SiO2)

Fossiliferous Limestone

Biogenic Limestone (Calcium Carbonate, CaCO3)

Chert Pebble

Microcrystalline or cryptocrystalline Quartz (SiO2)

Sandstone (Greywacke)

Arenite / Wacke (Mainly SiO2 with various lithic fragments)

Painted River Rock

Polished fluvial clast with acrylic/synthetic pigment coating

Sandstone (likely Fossiliferous Sandstone)

Clastic sedimentary rock (primarily SiO2)

Weathered basalt or mafic volcanic rock

Basalt; typically plagioclase feldspar, clinopyroxene, and often olivine or iron oxides

Sandstone

Arenite (composed primarily of SiO2)

Gneiss

Feldspar–quartz–mica gneiss, locally amphibole-bearing

Riverstone (likely Gray Slate or Siltstone)

Metamorphosed fine-grained sedimentary rock (Argillite/Slate)

Chert (Yellow Jasper/Flint)

Microcrystalline Quartz (SiO2)

Sandstone (likely Quartzose)

Arenite (primarily SiO2)

Small rounded pebble

Unidentified lithic clast; likely fine-grained sandstone, mudstone, or basalt

Fossilized Bone Chunk

Permineralized Vertebrate Bone (indeterminant)

Chert on Volcanic Host Rock

Sedimentary Chert (SiO2) within Basalt or Andesite

Dark river pebble (likely basalt or andesite)

Fine-grained mafic/intermediate volcanic rock; commonly basalt (plagioclase ± pyroxene/olivine)

Sandstone (Quartz-rich)

Sandstone (SiO2 dominated)

Yellow Chalcedony (likely Carnelian or Agate)

Silicon dioxide (SiO2)

Chert (or Fossiliferous Limestone)

Microcrystalline Quartz (SiO2) / Calcium Carbonate (CaCO3)

Chert (specifically Jasper)

Silicon dioxide (SiO2) with iron oxide inclusions

Sandstone (Graywacke type)

Clastic Sedimentary Rock (Lithic Sandstone)

Fossiliferous limestone (likely ammonite/gastropod-bearing)

Bioclastic limestone; predominantly calcite (CaCO₃)

Vesicular Sandstone

Clastic Sedimentary Rock (Sandstone)

Pebble / Gravel

Clastic Sedimentary Specimen (likely Limestone or Quartzite base)

Sandstone (likely Arkose or Lithic)

Clastic sedimentary rock (primarily 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.

Sandstone

Arenite (SiO2 based with mineral cement)

Chert / Chalcedony (likely carnelian or flint variety)

Silicon Dioxide (SiO2)