Agate
Silicon Dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Category
Rock
Browse rock specimens identified by the Rock Identifier community.
Horn Coral Fossil
Rugosa (Tetracoralla)
fossil
Quartz with inclusions (likely Chlorite or Hornblende) and country rock
SiO2 (Quartz) with associated ferromagnesian minerals
Mineral/Igneous/Metamorphic association
River cobble (Greywacke/Sandstone)
Sandstone / Greywacke
sedimentary
Basalt with Quartz Veins
Basalt with Quartz or Calcite Veining
igneous
Conglomerate
Sedimentary conglomerate rock (siliceous/ferruginous clastic rock)
sedimentary
Sandstone (Lithic Wacke)
Clastic sedimentary rock (primarily SiO2 with rock fragments)
sedimentary
River Pebble (likely Quartzite or Diorite)
Metamorphosed Quartz-rich Rock / Intermediate Igneous Rock
metamorphic
River Rocks (Basalt and Sedimentary Stones)
Mafic Igneous Rock (Basalt) and Clastic Sedimentary Rock
igneous and sedimentary
Hag Stone
Perforated sedimentary rock (typically flint, chert, or limestone)
sedimentary
Fossiliferous Limestone
Biogenic Sedimentary Rock (CaCO3)
sedimentary
Banded Sedimentary Rock
Siliciclastic Sedimentary Rock
sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
sedimentary
Cannonball Concretion
Calcite-cemented sandstone concretion
sedimentary
Shark Tooth Fossil
Chondrichthyes tooth
fossil
Shark Tooth Fossil
Chondrichthyes fossilized tooth
fossil
Chalcedony
Silicon Dioxide (SiO2)
mineral
Glacial Cobble (likely Granitic or Gneissic)
Granite/Gneiss Glacial Erratic
igneous
Tumbled serpentine or serpentinite
Serpentine-group minerals, chiefly antigorite, lizardite, or chrysotile; approximate formula Mg₃Si₂O₅(OH)₄
metamorphic
Quartz Geode
Silicon Dioxide (SiO2) within a sedimentary or igneous host
sedimentary
Quartz Geode
Silicon Dioxide (SiO2)
mineral
Basalt with Amygdales
Amygdaloidal Basalt
igneous
Tumbled green stone, likely serpentine
Serpentinite; chiefly serpentine-group minerals (antigorite, lizardite, chrysotile)
metamorphic
Serpentine (polished/tumbled)
Serpentine-group minerals, chiefly antigorite, Mg₃Si₂O₅(OH)₄
metamorphic
Rounded basalt pebble
Fine-grained mafic volcanic rock, commonly basalt (plagioclase + pyroxene ± olivine)
igneous
Basalt
Mafic extrusive igneous rock
igneous
Basalt with Quartz Veining
Veined Basalt (composed primarily of plagioclase feldspar, pyroxene, and olivine with quartz/calcite infill)
igneous
Basalt with Quartz/Calcite Veins
Amygdaloidal Basalt (SiO2 or CaCO3 inclusions)
igneous
Quartzite River Pebble
Quartzite (primarily Silicon Dioxide, SiO2)
metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
metamorphic
Porphyritic Basalt (Drill Core)
Porphyritic Basalt with Plagioclase Phenocrysts
igneous
Ferruginous Sandstone (Ironstone)
Sandstone with Hematite/Goethite cement (SiO2 + FeO(OH))
sedimentary
Schist
Mica Schist (contains muscovite/biotite and quartz)
metamorphic
River Rock (Basalt or Sandstone)
Clastic Sedimentary Rock or Extrusive Mafic Igneous Rock
igneous or sedimentary
Sandstone (Ferruginous)
Arenite (Siliclastic Sedimentary Rock)
sedimentary
Chalcedony / Agate Pebble
Silicon Dioxide (SiO2)
mineral
Agate
Cryptocrystalline quartz, Chalcedony (SiO2)
mineral
Jasper Pebble
SiO2 (Microcrystalline Quartz)
sedimentary
Quartz Pebble
Silicon Dioxide (SiO2)
sedimentary
Mixed River Pebbles and Jasper
Siliciclastic sediment and microcrystalline quartz
sedimentary
Sandstone (with secondary weathering/concretion)
Arenite (composed primarily of Quartz, SiO2)
sedimentary
Granite Pebble
Felsic Igneous Rock (Granitic composition)
igneous