Rock (Likely Sedimentary)

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Quartz geode

Microcrystalline quartz (SiO₂), commonly with chalcedony and possible calcite inclusions

Fine-grained, foliated rock (possibly slate or phyllite)

Undetermined; likely slate or phyllite, composed mainly of quartz, mica, and chlorite

Rounded quartz-rich pebble, possibly chert or quartzite

Indeterminate; likely microcrystalline quartz (SiO₂) or quartzite

Fossil brachiopod shell

Brachiopoda; exact genus/species indeterminate

Chalcedony/Agate

Cryptocrystalline Silica (SiO2)

Vuggy Quartz on Matrix

Silicon Dioxide (SiO2)

Weathered sandstone or limestone fragment

Likely quartz-rich sandstone or micritic limestone; exact identification requires testing

Chert (Nodular)

Microcrystalline Silica (SiO2)

Weathered mafic rock, likely basalt

Basalt; primarily plagioclase feldspar, pyroxene, and minor olivine or iron oxides

Weathered quartz-bearing rock, possibly calcite vein fragment

Indeterminate; likely quartz (SiO₂) with carbonate minerals such as calcite (CaCO₃)

Quartz-rich chalcedony (likely silicified rock)

Microcrystalline quartz, SiO₂; possibly silicified limestone or jasper

Coal (likely Bituminous or Lignite)

Organic Sedimentary Rock (Carbonaceous)

Geode (Unopened)

Silicon Dioxide (SiO2) in sedimentary vugs

Sandstone River Pebble

Arenite (SiO2 predominantly)

Sandstone (Ferruginous)

Arenite with Iron-Oxide Cement

Quartz-rich mineral fragment

Quartz (silicon dioxide, SiO₂), possibly milky quartz

Quartz (Druzy)

Silicon Dioxide (SiO2)

Sandstone (likely Arkose or Lithic)

Clastic sedimentary rock (primarily SiO2)

River Stone (likely Andesite or Siltstone)

Intermediate Volcanic Rock / Fine-grained Sedimentary Rock

Rounded sedimentary pebble, likely mudstone or shale

Argillite/mudstone; predominantly compacted clay minerals with quartz and iron oxides

River Pebble (Gravel)

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

Sandstone (likely Conglomerate or Gritstone)

Arenite (SiO2 based)

Sandstone (likely Calcareous or Quartz-rich)

Arenite (SiO2 based typically)

Quartz (Small Fragment)

Silicon Dioxide (SiO2)

Weathered sandstone or iron-rich sedimentary rock

Indeterminate siliciclastic rock; likely quartz-rich sandstone with iron-oxide staining

Small tan rock fragment

Unidentifiable lithic fragment; mineral composition undetermined

Sandstone (likely Quartzose type)

Clastic sedimentary rock (primarily SiO2)

Smooth river pebble

Indeterminate lithology; likely fine-grained quartz-rich sandstone, siltstone, or weathered chert

River Pebble (Graywacke/Sandstone)

Lithic Sandstone

Sandstone

Arenite (primarily SiO2)

Fossiliferous Limestone

Fossiliferous Limestone (CaCO3)

Sandstone (likely Arkosic or Ferruginous)

Arenite (SiO2 with iron oxides or feldspar)

Quartz Vein in Siltstone

Silicon Dioxide (SiO2) within Sedimentary/Metamorphic Matrix

Fossiliferous Limestone

Calcareous Sedimentary Rock (CaCO3)

Vesicular Sandstone

Clastic Sedimentary Rock (Sandstone)

Siltstone or Limestone Beach Pebble

Siltstone / Micritic Limestone

Chert or siliceous limestone fragments

Microcrystalline quartz (chert) and/or calcarenite; exact identification is uncertain from the photograph

Sandstone

Arenite (primarily SiO2)

Sandstone (River Rock)

Arenite (composed primarily of SiO2)

Jasper (Iron-stained Chert)

Silicon Dioxide (SiO2) with iron oxide inclusions

Quartz-rich breccia or silicified breccia

Cryptocrystalline quartz/chalcedony (SiO₂) with iron oxides and dark lithic fragments; exact classification is uncertain from the photograph