Chert (Flint)
Chert (Cryptocrystalline variety of Quartz, SiO2)
sedimentary
Category
Organic (Anthropogenic)
Browse organic (anthropogenic) specimens identified by the Rock Identifier community.
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Fossilized Horn Coral
Rugosa (Tetracoralla)
fossil
Likely petrified wood or silicified fossil fragment
Silicified wood; predominantly microcrystalline quartz (SiO₂)
fossil
Megalodon Shark Tooth
Otodus megalodon
fossil
Petrified Wood
Silicified Wood / Xylopal (SiO2)
fossil
Septarian Nodule
Septarian Concretion (Calcite, Aragonite, and Limestone)
sedimentary
Fossilized Horn Coral
Rugosa (Rugose Coral)
fossil
Fossil Shark Tooth
Carcharodon carcharias (modern/recent) or similar Lamniform fossil
fossil
Petrified Wood
Silicified Wood (SiO2-dominant)
fossil
Ironstone Concretion (Limonite/Hematite Nodules)
Ironstone (principally Limonite FeO(OH)·nH2O or Hematite Fe2O3 mixed with silica/clay)
sedimentary
Jasper (Petrified Wood variant)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Quartz Geode
Silicon Dioxide (SiO2) within a secondary sedimentary structure
sedimentary
Grey and White Chert (Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Stromatolite (Jasper-replaced)
Fossilized Stromatolite (Cyanobacteria / Cryptozon / Silica SiO2)
sedimentary
Petrified Wood
Silicified Wood (SiO2)
metamorphic
Jasper (Red-Brown)
Silicon Dioxide (SiO2) with Iron Oxide impurities
sedimentary
Chert (Quartz Variety)
Microcrystalline Silica (SiO2)
sedimentary
Chert (Flint Pebbles)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Chert (specifically Tan/Yellow Chert)
Chert (Microcrystalline or Cryptocrystalline Silica, SiO2)
sedimentary
Fossiliferous Limestone / Petoskey Stone (Coral Fossil)
Hexagonaria percarinata / Calcite (CaCO3)
fossil
Petrified Wood
Silicified Wood (SiO2)
fossil
Petrified Wood
Silicified wood / Xylopal
fossil
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Banded Sedimentary Rock (Siltstone/Mudstone with concretion)
Siltstone with Ferruginous Banding
sedimentary
Chert (Smooth River Pebble)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Jasper with Quartz Vein
Silicon Dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Yellow Jasper (Iron-stained Chert)
Silicon Dioxide (SiO2) with iron oxide (Limonite/Goethite) inclusions
sedimentary
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Chert (Jasper-bearing)
Silicon dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Graphite-veined Quartzite
Meta-sedimentary Quartzite with Carbonaceous/Graphitic Inclusions (SiO2 + C)
metamorphic
Fossil Coral (Favosites Honeycomb)
Favosites (Genus), Phylum Cnidaria, Class Anthozoa
sedimentary
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Jasper (Iron-stained Chert)
Silicon Dioxide (SiO2) with impurities of Hematite or Goethite
sedimentary
Anthracite Coal
Anthracite (Carbon-based organic sedimentary rock transitioned to metamorphic)
metamorphic
Fossilized Wood (Petrified Wood)
Silicified Wood (primarily quartz/chalcedony replacing organic matter)
Sedimentary (with some aspects of mineral replacement)
Limestone River Pebble
Calcium carbonate (CaCO3) - micritic limestone
sedimentary
Shale with Vein Infillings
Shale (a fine-grained clastic sedimentary rock). The veins could be Calcite (CaCO3), Quartz (SiO2), or other minerals.
Sedimentary Rock
Tumbled amber
Fossilized tree resin; commonly succinite (organic resin, not a mineral)
fossil
Fossilized Brachiopod Shell / Mold
Phylum Brachiopoda (Fossilized organic matrix replaced by Silica/Calcite)
fossil
Bituminous Coal
Organic Sedimentary Rock (composed mostly of carbon with sulfur and hydrogen)
sedimentary
Septarian Nodule
Septarian Concretion (Calcite, Aragonite, and Limestone)
sedimentary
Veined Limestone
Sedimentary Calcite-Veined Rock (CaCO3)
sedimentary