Rock

Basalt

Extrusive Igneous Rock

Basalt Pebble

Extrusive Igneous Rock / Basalt

Serpentine

Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)3(Si, Al, Fe)2O5(OH)4

Granodiorite (Gneissic texture)

Granodiorite (containing Quartz SiO2, Plagioclase Feldspar, and Biotite)

Basalt (Vesicular)

Basalt (Extrusive Volcanic Rock)

Porphyritic basalt (likely porphyritic andesite)

Plagioclase-phyric volcanic rock; plagioclase phenocrysts in a dark, fine-grained groundmass

Red Jasper (Beach Pebble)

SiO2 (Microcrystalline Quartz with Hematite inclusions)

Sandstone

Clastic sedimentary rock (primarily SiO2)

Geode (Quartz / Chalcedony Geode)

SiO2 (Silicon Dioxide)

Weathered greenish rock fragment

Tentatively altered basalt or serpentinite; exact identification requires testing

Basalt with Quartz Vein

Extrusive Igneous Rock / Volcanic Rock

Quartzite Pebble

Quartzite (mostly SiO2)

River Rock with Quartz Vein

Basalt or Andesite with Quartz Veining

Quartz vein fragment

Milky quartz (SiO₂), with a tan, iron-stained host rock

Vesicular volcanic rock, likely scoria

Scoria (vesicular basalt or andesite; exact composition cannot be confirmed from the image)

Rounded gray-brown pebble

Indeterminate; likely weathered quartz-rich sandstone or fine-grained volcanic rock

Quartz Geode

Silicon Dioxide (SiO2)

Amphibolite

Amphibolite, typically composed mainly of hornblende and plagioclase feldspar

Rounded brown pebble

Unidentified lithic pebble; composition cannot be determined from the image

Jasper and Quartz Breccia

Silicified Breccia (Quartz / Chalcedony / Hematite)

Gneiss (rounded cobble)

Quartz–feldspar–mica gneiss; exact mineral proportions cannot be determined from the image

Granite boulder

Granite, a coarse-grained felsic intrusive igneous rock composed mainly of quartz, feldspar, and mica

Weathered granite or granitic gneiss boulder

Granite; predominantly quartz, feldspar, and mica (exact identification is uncertain from a photograph)

Granite-like rock

Felsic intrusive igneous rock, probably granitic or granodioritic

Smooth river pebble, likely quartz-rich sandstone or quartzite

Probable quartz arenite (sandstone) or quartzite; mainly SiO₂ with minor iron-bearing minerals

Weathered greenstone (altered mafic rock)

Greenschist-facies metabasalt; typically chlorite, actinolite, epidote, and albite

Sandstone Cobble with Iron Staining

Arenite with Limonite/Hematite staining

Red Sandstone

Arenite (Iron-rich)

Polished dark-speckled igneous pebble, likely diorite or gabbro

Probable diorite (plagioclase feldspar and hornblende/biotite); exact identification is uncertain from the image

River Pebble (Siltstone / Fine Sandstone)

Sedimentary Rock (siliciclastic clastic rock)

Rounded brown river pebble

Indeterminate lithic clast; possibly weathered sandstone or fine-grained volcanic rock

Petrified Wood

Silicified wood (primarily quartz, SiO2)

Fossilized Bark

Lepidodendron / Sigillaria fossil impression

River Pebble (likely Quartzite or Siltstone)

Sedimentary Clast (SiO2 based)

River Rock

Mixed lithology clast

Painted River Pebble (likely Basalt or Greywacke)

Aphanitic Lithic Clast with Anthropogenic Pigment coating

Small red-brown mineral or rock fragment

Unidentified; possibly iron-oxide-rich jasper, garnet, or weathered sulfide

Sandstone (with Rock Art)

Sandstone (Clastic Sedimentary Rock)

Fossil-bearing limestone (probable)

Limestone, chiefly calcite (CaCO₃), with a visible spiral fossil that may be a gastropod

River-worn Chert

Microcrystalline Quartz (SiO2)

Quartz Pebble

Silicon Dioxide (SiO2)

Quartz Pebble (Feldspathic / Chert Pebble)

Silicon Dioxide (SiO2) / Potassium Feldspar (KAlSi3O8)