Igneous Or Sedimentary (Water Worn)

Carnelian (Tumbled)

Carnelian (Chalcedony / Silicon Dioxide, SiO2)

Rounded iron-rich stone, likely weathered basalt or laterite

Probable fine-grained basalt; reddish coloration may reflect hematite/goethite weathering

Orbicular rhyolite (likely)

Rhyolite, a silica-rich volcanic rock; commonly quartz, alkali feldspar, plagioclase, and iron-rich alteration minerals

Brown Pebble (Probable Chert or Siltstone)

Silicon Dioxide (SiO2) / Sedimentary Microcrystalline Quartz

Quartz Pebble

Silicon Dioxide (SiO2)

Yellow Quartz Pebble

SiO2 (Silicon Dioxide)

Quartz Pebble

Silicon Dioxide (SiO2)

Jasper or Red Quartzite

SiO2 (Silicon Dioxide with iron oxide impurities)

Banded Chert

Silicon Dioxide (SiO2)

Granite (Pink/Red variety)

Felsic Intrusive Igneous Rock

Jasper

Silicon Dioxide (Microcrystalline Quartz, SiO2)

Milky Quartz Pebble

Silicon Dioxide (SiO2)

Wishing Stone (Graywacke with Quartz Vein)

Graywacke Sandstone containing a Quartz (SiO2) intrusion

Quartz Pebble

Silicon Dioxide (SiO2)

River Pebble (likely Quartzite or Chert)

Sedimentary Clast (Silicon Dioxide dominant)

Pebble

Lithified rock fragment / Sedimentary clast

Banded Basalt / Lave Stone or Gneiss Pebble

Igneous/Metamorphic banded pebble

Milky Quartz Pebble

Silicon Dioxide (SiO2)

Riverstone Jasper

Silicon Dioxide (SiO2) with iron/clay inclusions

Quartz Pebble

Silicon Dioxide (SiO2)

Polished banded stone, likely gneiss or metasedimentary rock

Banded gneiss (quartz–feldspar–mica assemblage; exact identification requires testing)

White quartz pebble

Quartz (SiO₂), likely milky quartz

Gneiss (Gneissic Granite Pebble)

Metamorphic rock rich in Quartz, Feldspar, and Mica

Diorite (River Cobble)

Diorite (Intrusive Igneous Rock)

Jasper

Silicon dioxide (SiO2)

Basalt River Cobble

Basalt (Aphanitic Mafic Volcanic Rock)

Basalt with Quartz Vein

Basalt (extrusive igneous rock) with Quartz (SiO2) inclusion

Porphyritic basalt (vesicular basalt)

Basalt; fine-grained mafic rock, commonly composed of plagioclase, clinopyroxene, olivine, and iron-titanium oxides

Rounded dark river cobble

Likely basalt (fine-grained volcanic rock); exact identification is uncertain from the image alone

Granite pebble

Granite, a coarse-grained felsic intrusive igneous rock

Porphyritic Basalt or Andesite

Porphyritic Basalt/Andesite

Wishing Stone (Basalt with Quartz Vein)

Basalt with Hydrothermal Quartz Infill (SiO2)

Basalt (Water-worn)

Aphanitic Mafic Igneous Rock

Weathered iron-rich metamorphic rock (probable amphibolite or schist fragment)

Likely hornblende–plagioclase amphibolite with biotite/chlorite alteration; exact identification requires testing

Milky Quartz Pebble

Silicon Dioxide (SiO2)

Milky Quartz in Epidote Host Rock

Crystalline Silicon Dioxide (SiO2) with Epidote Ca2(Al,Fe)3(SiO4)3(OH)

Banded Chert or Mudstone

Chert (Silicon dioxide, SiO2) or Mudstone

Sandstone Pebble (Ventifact)

Arenite (mostly SiO2)

Chert (River Pebble)

Microcrystalline silica (SiO2)

River Stone (Greywacke)

Greywacke (immature sandstone)

Common River Pebbles and Stones

Mixed natural stream gravel / siliciclastic pebbles

Wishing Stone (Sandstone with Quartz Vein)

Arenite with Quartzite intrusion (SiO₂)