Septarian Nodule (or Mudstone with Septarian Cracking)
Septarian Concretion (Composition: Calcite, Aragonite, and Limestone/Claystone)
sedimentary
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.
Tektite (likely Australite)
Tektite (no specific chemical formula as it's a natural glass of variable composition, mostly SiO2, Al2O3, FeO, MgO, CaO, K2O, Na2O, TiO2)
Mineral (specifically a mineraloid)
Conglomerate
Conglomerate (clastic sedimentary rock)
sedimentary
Conglomerate
Clastic Sedimentary Rock (Conglomerate)
sedimentary
Celestite (Celestine)
Strontium sulfate (SrSO4)
mineral
Sandstone (with Iron Staining)
Clastic sedimentary rock (primarily Quartz with Fe2O3 staining)
sedimentary
Limestone (Grey and White specimens)
Calcium Carbonate (CaCO3)
sedimentary
Ironstone (likely Limonite or Goethite)
Ferruginous sedimentary rock (FeO(OH)·nH2O)
sedimentary
Pink Granite
Granite (Felsic Plutonic Rock)
igneous
Conglomerate
Conglomerate (clastic sedimentary rock)
sedimentary
Agate and Amethyst (Quartz variants)
Silicon Dioxide (SiO2) - Microcrystalline Quartz and Crystalline Quartz
mineral
Limestone
Calcareous sedimentary rock (CaCO3)
sedimentary
Ironstone (likely siderite or goethite-rich siltstone)
Ferruginous Siltstone
sedimentary
Piddock bored rock (likely Mudstone or Shale)
Ichnofossil (Gastrochaenolites borings) in Fine-grained Sedimentary Rock
sedimentary
Quartz in Matrix (possibly with Biotite or Hornblende)
Quartz (Silicon Dioxide, SiO2) in Granitic Matrix
igneous
Chert (Flint Nodules)
Cryptocrystalline Quartz (SiO2)
sedimentary
Sandstone with Liesegang Rings
Arenite with Iron Oxide Concretions
sedimentary
Sapphire (likely blue synthetic sapphire or blue glass in a ring)
Corundum (Al₂O₃), specifically the blue variety due to trace amounts of iron and titanium impurities. If synthetic, it would still be Al₂O₃.
Mineral
Carnelian (Red Chalcedony)
Silicon Dioxide (SiO2)
mineral
Pink Granite
Phaneritic Felsic Igneous Rock (composed primarily of K-Feldspar, Quartz, and Mica)
igneous
Chert (specifically Yellow or River Chert)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Sandstone (Greywacke)
Arenite / Wacke (Mainly SiO2 with various lithic fragments)
sedimentary
Chert (specifically Tan/Gray Chert)
Microcrystalline quartz (SiO2)
sedimentary
Conglomerate
Clastic sedimentary rock (Polymictic Conglomerate)
sedimentary
Conglomerate
Conglomerate (Sedimentary rock containing rounded clasts)
sedimentary
Chert (specifically Jasper or Brown Chert node)
Microcrystalline Quartz (SiO2)
sedimentary
Limestone
Calcareous Sedimentary Rock (CaCO3)
sedimentary
Quartz Geode
Silicon Dioxide (SiO2)
mineral
Painted River Pebble (likely Basalt or Greywacke)
Aphanitic Lithic Clast with Anthropogenic Pigment coating
Sedimentary or Igneous
Banded Iron Formation
Banded Iron Formation (BIF)
Metamorphic Rock
Concrete Paver (Artificial Cementitious Rock)
Hydrated Portland Cement Aggregate
Sedimentary (Synthetic)
Chert (specifically Flint or Jasper variant)
Microcrystalline Quartz (SiO2)
sedimentary
Orange Calcite
Calcium Carbonate (CaCO3)
mineral
River/Stream Pebble
Clast / Detrital Grain / Rounded Sedimentary Particle (Compositionally variable, commonly Quartz, Feldspar, Chert, or other resistant rock fragments)
Mineral, specifically a rock fragment
Amethyst
Silicon Dioxide with Iron impurities (SiO2 + Fe3+)
mineral
Amethyst
SiO2 (Silicon Dioxide with Iron impurities)
mineral
Conglomerate
Conglomerate (clastic sedimentary rock)
sedimentary
Quartz (likely Jasper or Chert variety)
Quartz (SiO₂)
Mineral
Quartz Geode (Cracked)
Quartz (Silicon Dioxide, SiO2)
sedimentary
Citrine (Heat-Treated Amethyst)
Silicon Dioxide (SiO2)
mineral
Chert (specifically Agate/Jasper variety)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Chalcedony (Botryoidal or Geode form)
Silicon Dioxide (SiO2)
mineral