Not A Rock

Granite

Intrusive Igneous Rock

Basalt Pebble

Extrusive Igneous Rock (Mafic)

Basalt

Extrusive mafic igneous rock

Breciated Jasper

Silicon Dioxide (SiO2) with iron oxide inclusions

Banded Gneiss / Veined Metamorphic Pebble

Metamorphic Rock with Quartz/Feldspar Veins

Lapis Lazuli

Lapis Lazuli (a rock type, not a single mineral; main component is Lazurite (Na,Ca)8[(S,Cl,SO4,OH)2|(Al6Si6O24)])

Sandstone (likely Greywacke or Lithic Sandstone)

Arenite / Wacke

Biotite-bearing granite

Granite, composed chiefly of quartz, feldspar, and biotite; exact identification is uncertain from the photo.

Feldspathic gneiss (likely augen gneiss)

Quartz–feldspar–mica gneiss; commonly dominated by quartz, K-feldspar/plagioclase, and biotite

Granite fragment (tentative)

Granite; primarily quartz (SiO₂), feldspar, and mica

Granite / granitic gneiss boulders

Granite, primarily quartz, feldspar, and mica; some pieces may be foliated granitic gneiss

Light-colored granite or granitic gneiss

Granite; typically quartz + feldspar + mica (variable composition)

Generic Rock Fragment

Rock Fragment

Pebble (Likely Basalt or Siltstone)

Clastic sedimentary rock or mafic volcanic rock

Banded agate (likely botryoidal chalcedony)

Agate, microcrystalline quartz (SiO₂), commonly chalcedony with quartz bands

Sandstone with Iron Banding

Arenite with Hematite or Limonite staining (SiO2 with Fe2O3)

Greenish altered rock, possibly serpentinite or chlorite-rich schist

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

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Greenstone (likely altered mafic rock)

Chlorite- and amphibole-bearing metabasalt; exact identification requires testing

Yellow Chert or Jasper

Microcrystalline Quartz (SiO2)

River Pebble (Quartz/Jasper)

Silicon Dioxide (SiO2)

Quartz Pebble

Silicon Dioxide (SiO2)

Fossiliferous Chert with Brachiopod Impression

Chert (SiO2) containing Brachiopoda fossil remains

Pebble (likely a type of sandstone or quartzite pebble)

Clastic Sediment (specifically, a rudite-sized clast). If the pebble is composed of a specific rock type, its scientific name would be that rock type (e.g., 'Quartzite pebble', 'Granite pebble', 'Chert pebble'). Given its appearance, it is likely a metamorphic quartzite pebble or a hard sandstone pebble.

Sandstone or Mudstone

Sedimentary Rock

Conglomerate

Conglomerate Rock

Conglomerate

Conglomerate Rock

Porphyry

Porphyritic Rock

Conglomerate

Conglomerate rock

Granite

Felsic intrusive igneous rock

Greenish metamorphic rock (possibly chlorite schist)

Chlorite-rich schist; exact identification is uncertain from the image

Quartz-bearing rock fragment

Likely quartz with iron-oxide staining; exact rock type cannot be determined from the image

Shale

Lutaceous sedimentary rock

Bivalve Seashell Fossil

Class Bivalvia

Rhyolite with Lithophysae and Iron Oxide

Extrusive igneous rock / Felsic volcanic rock

River Stone (Basalt or Siltstone)

Mafic Volcanic Rock or Clastic Sedimentary Rock

Weathered sandstone block

Quartz-rich sandstone; exact composition cannot be confirmed from the image

Quartz Vein in Basalt

Silicon Dioxide (SiO2) in Mafic Igneous Rock

Painted River Rock

Painted Quartzite or Smooth Siltstone

Quartz-rich gravel fragment

Quartz (silicon dioxide, SiO₂), possibly with feldspar or carbonate inclusions

Weathered granite

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

Biotite-bearing granite or granitic gneiss

Quartz–feldspar–biotite granitoid; exact identification requires testing