Rock (Likely Sedimentary)

Small rounded pebble (rock type indeterminate)

Unidentified lithic pebble; specific composition cannot be determined from the image

Fossil gastropod shell

Fossilized gastropod, likely a small marine snail; exact genus cannot be determined from the image

Rounded gray river pebble, likely fine-grained basalt or andesite

Basaltic-andesitic volcanic rock; commonly plagioclase feldspar, pyroxene, and minor iron oxides

Likely mica-rich metamorphic rock (schist)

Mica schist, probably containing muscovite and/or biotite with quartz and feldspar

Quartz-rich sandstone (probable)

Quartz arenite; predominantly quartz (SiO₂) grains

Gray Limestone

Carbonate rock (CaCO3)

Conglomerate

Clastic sedimentary rock (Psephite)

Pumice

Pumice (Amorphous volcanic glass)

Sandstone

Clastic sedimentary rock (primarily SiO2)

Likely bituminous coal

Coal, predominantly carbon-rich organic matter with variable maceral and mineral content

Sandstone (with carbonaceous plant fragments)

Arenite (composed primarily of SiO2)

Small pale stone, likely quartzite or limestone fragment

Indeterminate; possible quartzite (mostly SiO₂) or calcitic limestone (CaCO₃)

Tumbled quartz-rich pebble

Quartz (SiO₂), likely a rounded quartzite or quartz-rich sandstone pebble

Conglomerate

Conglomerate (clastic sedimentary rock)

Sandstone

Arenite

Weathered pebble, possibly quartz-rich river stone

Unidentified silicate rock; composition cannot be determined reliably from the image

Quartz geode

Microcrystalline and crystalline quartz, SiO₂, likely with chalcedony and iron-oxide staining

Sandstone Pebble

Arenite (Sandstone)

Mixed rough mineral specimens, likely quartz-bearing rocks

Probable quartz (SiO₂), with possible feldspar, iron oxides, and altered host rock

Painted River Rock

Artificially Coated Sedimentary Rock

Water-worn sandstone pebble

Quartz-rich sandstone (composition and exact subtype uncertain from image)

Unidentifiable embedded dark fragment

Indeterminate; possibly a dark silicate mineral or lithic inclusion

Fossil-bearing fine-grained sedimentary rock

Likely fossiliferous mudstone or shale; visible feature may be a plant fragment, trace fossil, or mineral vein

Likely quartz-bearing rock fragment

Quartz (SiO₂), possibly with iron-oxide staining or other mineral inclusions

Weathered banded gneiss

Foliated quartz–feldspar-rich gneiss; exact mineral identification requires closer examination

Chert (Yellow/Tan Variety)

Chert (SiO2)

Greywacke (likely)

Greywacke (a type of sandstone)

Conglomerate

Clastic Sedimentary Rock (Conglomerate)

Rounded river pebble (lithology unclear)

Indeterminate natural rock; no specific mineral or rock type can be identified from the image

Weathered yellow-brown rock pebble

Undetermined; possibly iron-oxide-stained sandstone or mudstone

Iron-rich banded rock, likely goethite/limonite-rich ironstone

Goethite (α-FeO(OH)) and/or limonite with iron-oxide-stained silica or clay; exact identification requires testing

Weathered porphyritic volcanic rock (likely basaltic andesite)

Porphyritic basaltic andesite; mineral assemblage likely plagioclase, pyroxene, and iron oxides

Conglomeratic sedimentary rock (likely breccia/conglomerate)

Poorly sorted clastic rock with mixed lithic fragments; exact lithology cannot be confirmed from the image

Small weathered rock fragment (likely sandstone)

Quartz-rich sandstone; exact identification is uncertain from the image

Sandstone (likely Graywacke or Lithic Sandstone)

Clastic Sedimentary Rock

River Rock (likely Siltstone or fine-grained Sandstone)

Clastic Sedimentary Rock

Rough amber-colored quartz or calcite fragment

Likely quartz (SiO₂) or calcite (CaCO₃); exact identification requires testing

Likely mica-rich schist

Mica schist, probably muscovite- or biotite-bearing; exact minerals cannot be confirmed from the photo

Likely mica-rich schist

Mica schist, probably muscovite- and/or biotite-bearing; exact identification requires closer examination

Fossil bivalve or brachiopod in sedimentary rock

Unidentified fossil shell impression; likely a ribbed bivalve or brachiopod preserved in shale/siltstone

Small quartz-rich mineral fragment

Quartz (SiO₂), possibly milky or chalcedonic quartz

Small iron-stained quartz-rich rock fragment

Likely quartz (SiO₂) with iron-oxide staining; exact identification is uncertain from the image