Greenschist
Greenschist (chlorite-epidote schist)
metamorphic
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.
Chert (varietal known as Jasper or Flint)
Silicon Dioxide (SiO2)
Sedimentary Rock
Quartz (Milky/Yellowish variety)
Silicon Dioxide (SiO2)
mineral
Granite Cobble
Granite (Felsic Plutonic Rock)
igneous
Granite Cobble
Felsic Intrusive Igneous Rock
igneous
Devil's Toenail
Gryphaea (extinct genus of foam oysters, typically composed of Calcite CaCO3)
sedimentary
Chert (often referred to as 'Jasper' when red)
Chert (microcrystalline quartz, SiO₂)
Sedimentary rock
Red Sandstone
Arenite (with Iron Oxide / Hematite), Formula: SiO2 (Quartz) + Fe2O3 (Hematite coating)
sedimentary
River Pebble (likely Quartzite or Chert)
Silicon Dioxide (SiO2)
metamorphic or sedimentary
Smoky Quartz and Chalcedony Geode Fragment
Silicon Dioxide (SiO2)
mineral
Chert (or Flint)
SiO2 (predominantly microcrystalline quartz)
Sedimentary
Granite Cobble
Felsic Intrusive Igneous Rock (composed of Quartz, Alkali Feldspar, and Plagioclase)
igneous
Ferruginous Conglomerate
Conglomerate with Iron-Oxide Matrix (SiO2 + Fe2O3/FeO(OH))
sedimentary
Quartzite River Rock
Quartzite (primarily SiO2)
metamorphic
Quartz
Quartz (SiO₂)
Mineral
Granite Cobble
Phaneritic Felsic Igneous Rock (primarily Quartz, Feldspar, and Mica)
igneous
Druzy Quartz on Chert/Siltstone
Silicon Dioxide (SiO2) on Microcrystalline Silica/Siltstone matrix
sedimentary
Banded Gneiss (River Rock/Pebble)
Gneiss (specifically a banded variety often found as a river rock)
Metamorphic Rock
Agate
Silicon Dioxide (SiO2) - variety Chalcedony
mineral
Basalt
Basalt (Mafic volcanic rock)
igneous
Banded Gneiss
Gneiss (High-grade metamorphic rock typically composed of Quartz, Feldspar, and Mica)
metamorphic
Quartzite River Rock
Metamorphic Quartzite (primarily SiO2)
metamorphic
Chert (Chert / Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Greywacke (River Pebble)
Greywacke sandstone with quartz veining
sedimentary
Shale
Lutaceous Sedimentary Rock
sedimentary
Basalt
Basalt (Extrusive Mafic Igneous Rock)
igneous
Grooved Maun Ball (Maul/Hammerstone-like Concretion)
Calcareous/Ferruginous Concretion in Sandstone Matrix
sedimentary
Chert
Chert (variant of microcrystalline quartz)
Sedimentary
Grey Limestone Pebble
Limestone (Calcium Carbonate - CaCO3)
sedimentary
Quartzite with Feldspar
Quartzite (mainly SiO2) with inclusions of Potassium Feldspar (KAlSi3O8)
metamorphic
Fossil Bivalve Shell
Class Bivalvia (e.g., Veneriidae family)
sedimentary
Basalt
Basalt
igneous
Serpentine
Serpentine-group ((Mg,Fe,Ni,Al,Zn,Mn)3(Si,Al,Fe)2O5(OH)4)
metamorphic
Shale
Fissile Mudstone
sedimentary
River Pebble (Quartzite/Siltstone mixture)
Silicon Dioxide (SiO2) mixture with varied clastic minerals
sedimentary/metamorphic
River Cobble (likely Basalt)
Mafic Igneous Rock (Aphanitic)
Igneous
Metaconglomerate
Protolith: Conglomerate (comprising SiO2, Al2O3, etc.)
metamorphic
Green Porphyry (Flowerstone)
Porphyritic Andesite or Basalt
igneous
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Quartz Geode
Silicon Dioxide (SiO2) within a geode
mineral
Fossiliferous Limestone (Coquina / Shell Limestone)
Bioclastic Limestone (CaCO3)
sedimentary
Basalt River Cobble
Basalt (Composition primarily Plagioclase Feldspar and Pyroxene)
igneous