Chert (Nodule)
Microcrystalline or Cryptocrystalline Silica (SiO2)
sedimentary
Category
Sedimentary Rock (Specifically A Clastic Sedimentary Rock Formed Into A Cobble)
Browse sedimentary rock (specifically a clastic sedimentary rock formed into a cobble) specimens identified by the Rock Identifier community.
Vesicular Basalt (Scoria)
Extrusive Mafic Igneous Rock (primarily Plagioclase Feldspar and Pyroxene)
igneous
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Quartzite River Rock
Quartzite (SiO2)
metamorphic
Banded Gneiss (River Rock/Pebble)
Gneiss (specifically a banded variety, likely a orthogneiss or paragneiss depending on parent rock)
Metamorphic Rock
Fire Opal (in Matrix)
Hydrated Silica (SiO2·nH2O)
mineral
Druzy Quartz on Chalcedony Matrix
Silicon Dioxide (SiO2)
mineral
Agate (Common Chalcedony)
Silicon Dioxide (SiO2)
mineral
Asphalt Chunk (with aggregate)
Bituminous concrete / Anthropogenic conglomerate
sedimentary (anthropogenic/man-made conglomerate)
Caribbean Calcite
Calcium Carbonate with Argonite (CaCO3)
mineral
Porphyritic Basalt (Chinese Flower Stone / Chrysanthemum Stone basalt variety)
Porphyritic Basalt containing Plagioclase Feldspar phenocrysts
igneous
Ocean Jasper
Spherulitic Chalcedony (SiO2)
mineral
Gneiss (Pebble)
Gneiss
metamorphic
River Rock (Basalt/Greywacke pebbles)
Fluvial gravel primarily composed of Mafic Volcanic Rock (Basalt) or Lithic Sandstone (Greywacke)
igneous and sedimentary
Banded Slate or Siltstone with Quartz/Calcite Veins
Protolith-derived Siltstone or Slate (varies based on degree of metamorphism)
metamorphic
Chert (or possibly Flint)
SiO2 (Silicon Dioxide)
Sedimentary Rock
Pink Granite
Felsic intrusive igneous rock
igneous
Basalt River Cobble
Basalt (Aphanitic Mafic Volcanic Rock)
igneous
Basalt
Basalt (composition of plagioclase feldspar and pyroxene)
Igneous
Serpentine (Nephrite-like River Cobble)
Serpentinite (Hydrous Magnesium Iron Silicate)
metamorphic
Quartzite
Quartzite (primarily SiO2)
metamorphic
Basalt River Cobble
Vitreous aphanitic Basalt
igneous
Marble
Recrystallized Calcite (CaCO3) Rock
metamorphic
Chert (Nodule)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Concretion
Various mineral compositions, typically carbonate or iron oxide cemented sediment
Sedimentary
Basalt (Polished River Stone)
Mafic Volcanic Rock (primarily Plagioclase and Pyroxene)
Igneous
Biotite (Black Mica)
Biotite - K(Mg,Fe)3AlSi3O10(F,OH)2
mineral
Pebble (likely Quartzite or Chert)
Clastic Sediment, potentially composed of SiO₂ (Quartz)
Mineral, Sediment
Quartz (Druzy on Matrix)
Silicon Dioxide (SiO2)
mineral
Diorite (River Cobble)
Phaneritic Intermediate Plutonic Rock
igneous
Agate
Silicon Dioxide (SiO2) - Microcrystalline Quartz
sedimentary
River Quartz Pitting/Cobble
Silicon Dioxide (SiO2)
mineral
Diorite
Diorite (Intermediate intrusive igneous rock)
igneous
Geode (Unopened)
Silica-rich concretion (SiO2)
sedimentary
Green Aventurine
Aventurine Quartz (SiO2 with inclusions)
metamorphic
Quartzite River Rock
Quartzite (primarily SiO2)
metamorphic
Quartzite with Iron Hydroxide Staining
Quartzite (primarily SiO2) with Limonite/Goethite staining
metamorphic
River Cobble (likely Basalt or Chert)
Siliceous River Rock / Microcrystalline Quartz / Mafic Igneous
igneous/sedimentary
Quartzite
Quartzite (primarily SiO2)
metamorphic
Porphyritic Rhyolite (Birdseye Rhyolite)
Rhyolite (Porphyritic texture)
igneous
River Rock (Glacial Cobbles)
Fluvial Alluvium (Mixed lithology including Quartzite, Basalt, and Granite)
Mixed (predominantly sedimentary and igneous)
Ironstone Concretion (Ironstone Gourd)
Limonite/Goethite Concretion (FeOO(H))
sedimentary