Industrial Byproduct (Anthropogenic Rock)

Quartz in Granite

SiO2 embedded in felsic intrusive rock

Agate

Chalcedony (SiO2)

Agate

Silicon dioxide (SiO2)

Waterworn pebble, possibly iron-rich basalt or river stone

Unidentified lithic clast; composition cannot be determined reliably from the image

Garnet

Silicate mineral group (e.g., Almandine, Fe3Al2(SiO4)3)

Small tan rock fragment

Unidentifiable lithic fragment; mineral composition undetermined

Quartzite

Quartzite (SiO2)

Bituminous Coal

Coal (Sedimentary Rock)

Concretion or weathered iron-rich rock

Likely limonite/goethite-rich concretion; exact identification requires testing

Rounded pale-green pebble, likely serpentinite or altered basalt

Probable serpentinite (serpentine-group minerals) or weathered mafic rock; exact identification requires testing

Small rounded rock (likely granite or gneiss)

Unidentified coarse-grained silicate rock; likely granitic composition

Small polished pebble, likely quartz or quartzite

Undetermined; possibly quartzite (quartz, SiO₂)

Basalt

Extrusive mafic igneous rock

Sandstone (lithic wacke)

Arenite / Lithic Wacke (mostly SiO2 with rock fragments)

Granodiorite

Granodiorite

Milky Quartz with Iron Staining

Silicon Dioxide (SiO2)

Quartz Pebble

Silicon Dioxide (SiO2)

Sandstone

Arenite (SiO2 based with quartz grains)

Vesicular Basalt

Aphanitic Mafic Volcanic Rock

Greenish altered rock, possibly serpentinite or chlorite-rich schist

Tentative: serpentine-group minerals, chiefly antigorite/lizardite, or chlorite–actinolite assemblage

Tumbled yellow jasper (probable)

Jasper, an opaque microcrystalline variety of quartz; chiefly SiO₂ with iron-oxide inclusions

Crushed Stone (Basalt/Gabbro)

Mafic Igneous Rock (primarily Plagioclase and Pyroxene)

Unidentified rough rock fragment

Indeterminate; no diagnostic mineral or texture can be confirmed from the image

Rounded tan pebble

Unidentified fine-grained rock; the image does not show enough detail for a reliable species-level identification.

Basalt Water-Worn Pebble

Aphanitic Mafic Igneous Rock

Scoria

Scoria (vesicular volcanic rock)

Vesicular Basalt (or Scoria)

Extrusive mafic igneous rock

Quartz Vein with Host Rock (Greywacke/Siltstone)

Silicon Dioxide (SiO2) within Clastic Sedimentary/Metamorphic Matrix

Granitic Pegmatite

Pegmatite

Tumbled milky quartz

Quartz, silicon dioxide (SiO₂)

Pegmatite

Intrusive Igneous Rock

Rock specimen shown in a classroom identification activity

Undetermined; the pictured specimen may be a fine-grained, pinkish rock, but the image does not provide enough detail for a reliable identification

Gravel and Sediment Sample

Mixed clastic sediment

Native Copper in Matrix

Native Copper (Cu)

Sedimentary Rock

Sedimentary rock (lithified sediment)

Rounded, mottled river pebble

Unidentified fine-grained rock; the image is insufficient for a reliable species-level identification

Basalt (River Stone)

Basalt

Clear quartz (rock crystal)

Quartz, crystalline silicon dioxide (SiO₂)

Small weathered rock fragment

Unidentified lithic fragment; composition cannot be determined from the image

Garnet Schist

Almandine Garnet Schist (Fe3Al2(SiO4)3 in Schistose matrix)

Coal

Bituminous coal (Complex organic sedimentary rock)

Sandstone

Arenite (primarily SiO2)