Biotite granite (weathered granitic rock)
Granite; chiefly quartz (SiO₂), feldspar, and biotite mica
igneous
Category
Sedimentary Rock (Specifically A Concretion Or Possibly A Geode)
Browse sedimentary rock (specifically a concretion or possibly a geode) specimens identified by the Rock Identifier community.
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Quartz Geode (Druzy)
Crystalline Silicon Dioxide (SiO2)
mineral
Clear Quartz (Rock Crystal)
Silicon Dioxide (SiO2)
mineral
Geode
Quartz / Chalcedony nodule
sedimentary
Geode with Quartz and Chalcedony
Silicon Dioxide (SiO2)
sedimentary
River Cobble (Basaltic/Andesitic)
Mafic Igneous Porphyritic Rock
igneous
Likely basalt or other dark igneous rock
Basalt; predominantly plagioclase feldspar and pyroxene, possibly olivine
igneous
Chert (Flint)
Silicon Dioxide (SiO2)
sedimentary
Basalt
Basalt
igneous
Basalt (Vesicular)
Basalt (Mafic Extrusive Igneous Rock)
igneous
Weathered iron-rich rock, possibly jasper or ironstone
Likely limonite/goethite-bearing siliceous rock; exact identification requires hardness and streak tests
mineral
Quartz Veined Rock (Likely Graywacke or Quartzite)
Silicon Dioxide (SiO2) veins in Metasedimentary matrix
metamorphic
Brecciated jasper/chalcedony (iron-stained silica)
Microcrystalline quartz, SiO₂, with iron-oxide inclusions
mineral
Quartz Geode (partially opened)
Silicon Dioxide (SiO2) with iron staining
mineral
Clear Quartz (Rock Crystal)
Silicon Dioxide (SiO2)
gemstone
Quartz (Druzy)
Silicon Dioxide (SiO2)
mineral
Agate Geode
Silicon Dioxide (SiO2) - Chalcedony / Quartz Variety
Mineral
Celestine (Celestite)
Strontium sulfate (SrSO4)
mineral
Quartz Pebble (Geode-like)
Silicon Dioxide (SiO2)
Mineral
Quartz Druzy Geode
Silicon Dioxide (SiO2)
mineral
Pyrite-rich Ore
Pyrite (FeS2) with secondary minerals
mineral
Carnelian
Chalcedony (SiO2) with Iron Oxide inclusions
mineral
Chalcedony (Quartz)
Silicon dioxide (SiO2)
mineral
Quartz Geode Fragment
Silicon Dioxide (SiO2)
mineral
Basalt Porphyry
Porphyritic Basalt
igneous
Thunderegg (Agate or Quartz Geode)
Silica-filled rhyolitic nodule (SiO2)
sedimentary
Sandstone (specifically Banded Sandstone)
Clastic sedimentary rock (primarily SiO2)
sedimentary
Amethyst
Amethyst (Silicon Dioxide - SiO2 with impurities of iron)
mineral
Amethyst Geode Fragment
Amethyst (Silicon Dioxide, SiO2) with Quartz matrix
mineral
Basalt (Greenstone)
Amygdaloidal Basalt / Chloritized Basalt
Igneous
Weathered limestone or calcareous concretion
Calcite-rich carbonate rock; primarily calcium carbonate (CaCO₃), commonly calcite
sedimentary
Sandstone Concretion
Sedimentary Concretion (SiO2 or CaCO3 cemented)
sedimentary
Weathered sandstone or iron-stained sedimentary rock
Likely quartz-rich sandstone; exact identification is uncertain from the photograph
sedimentary
Banded Gneiss
Gneiss (High-grade regional metamorphic rock)
metamorphic
River Rock / Stream Pebble
Fluvial Clast / Rounded Sedimentary Particle
Sedimentary Rock (possibly composed of various minerals)
Chert (Jasper variety)
Microcrystalline Quartz (SiO2)
sedimentary
Quartz-rich mineral fragment
Quartz (silicon dioxide, SiO₂), possibly milky quartz
mineral
Chalcedony Nodule (Agate/Chert)
Chalcedony (cryptocrystalline Silicon Dioxide, SiO2)
mineral
Quartz Geode
Silicon Dioxide (SiO2)
mineral
Druzy Quartz (on Geode Fragment)
Silicon Dioxide (SiO2)
mineral
Chert / Flint
Cryptocrystalline Quartz (SiO2)
sedimentary
Weathered limestone
Calcite-rich limestone (CaCO₃), possibly fossiliferous or dolomitic
sedimentary