Rock (Likely Sedimentary)

River Cobble (Quartzite or Sandstone)

Clastic sedimentary rock (primarily SiO2)

Coarse-grained granite

Granite; predominantly quartz, potassium feldspar, plagioclase, and biotite/hornblende

Quartz-rich metamorphic rock, likely mica schist or quartzite

Quartz (SiO₂) with mica, feldspar, and possibly iron-oxide staining

Fossilized shell or small fossil fragment

Indeterminate fossil; possibly a partial gastropod or bivalve, mineralized with calcite

Rounded quartz-rich pebble

Quartz (SiO₂), possibly a quartzite or light-colored chert pebble

Black Opal

Hydrated Amorphous Silica (SiO2·nH2O)

Sandstone (Quartz Arenite)

Sandstone (SiO2 with possible mineral cements)

Sandstone (likely Quartzose Sandstone)

Arenite (primarily SiO2)

Likely weathered sandstone fragment

Sandstone, chiefly quartz (SiO₂) with feldspar and iron-oxide cement

Red aventurine quartzite (likely)

Quartzite; predominantly microcrystalline quartz (SiO₂) with iron-oxide and feldspar impurities

Sandstone (Weathered Pebble)

Arenite (primarily SiO2)

Sandstone (likely Graywacke or Arkose variant)

Clastic Sedimentary Rock (SiO2 dominated)

Rounded river pebble

Likely quartz-rich sandstone or weathered chert; exact identification requires testing

Sandstone (likely Quartz Sandstone)

Arenite (SiO2 based)

Feldspathic Gneiss

High-grade Metamorphic Rock (Gneiss)

Milky quartz-rich rock

Quartz, SiO₂; possibly quartzite or massive vein quartz

Weathered quartz-rich cobble (probable sandstone or quartzite)

Indeterminate; likely quartz arenite sandstone, possibly weakly metamorphosed quartzite

Chert (often called Jasper or Flint)

Microcrystalline Quartz (SiO2)

Amethyst Geode Fragment

Amethyst (Silicon Dioxide, SiO2) with Quartz matrix

Chalcedony (Agate)

Silicon Dioxide (SiO2)

Metallic sulfide ore, likely pyrite-bearing rock

Pyrite (FeS₂), possibly with chalcopyrite and quartz/host rock

Sandstone

Arenite (SiO2 based with mineral cement)

Weathered brown rock, likely sandstone or iron-rich quartzite

Indeterminate; probable quartz-rich sandstone (quartz, feldspar, iron oxides)

Sandstone

Arenite (SiO2 dominant)

Sandstone (likely Fossiliferous)

Arenite / Sedimentum arenaceum

Sandstone (with Iron Staining)

Clastic sedimentary rock (primarily SiO2 with Fe2O3 oxides)

Rounded river pebble

Indeterminate; likely quartz-rich sandstone, chert, or weathered volcanic rock

Weathered basalt boulder

Basalt; fine-grained mafic volcanic rock, chiefly plagioclase and pyroxene with possible olivine

Tumbled quartz-rich pebble

Microcrystalline quartz (SiO₂), possibly milky quartz or chalcedony

Quartz Geode

Silicon Dioxide (SiO2)

Likely fossil oyster shell

Fossilized bivalve shell; exact species cannot be identified from the image

Pink feldspar-rich granite or pegmatite

Potassium-feldspar granite; chiefly microcline/orthoclase (KAlSi₃O₈), quartz, and minor mica

Sandstone (likely Quartzose Sandstone)

Arenite (composed primarily of SiO2)

Likely weathered sandstone or iron-rich sedimentary rock

Quartz-rich sandstone, possibly ferruginous sandstone

Black-and-white veined stone, likely marble or calcite-veined metamorphic rock

Probable calcite marble: predominantly recrystallized calcite (CaCO₃) with dark graphite-, mica-, or amphibole-rich minerals

Rounded granitic pebble (likely granite or granodiorite)

Granite–granodiorite; chiefly quartz, feldspar, and mica/amphibole

Sandstone with Magnetite and Iron Staining

Clastic Sedimentary Rock (contains Fe3O4 and Limonite/Hematite)

Jasper

Silicon dioxide (SiO2) with impurities

Unidentified gray-brown stone

Likely fine-grained quartz–feldspar rock; exact identification is not possible from this close, blurred image

Quartz geode / druzy quartz

Quartz (SiO₂), likely a small chalcedony-lined geode with drusy quartz crystals

Sandstone (Quartz-rich)

Sandstone (SiO2 dominated)

Sandstone (likely Quartzose)

Arenite (SiO2 principal mineral)