Ammonite Fossil
Ammonoidea (primarily composed of Calcite, CaCO3)
sedimentary
Category
Organic Gemstone (Fossilized Resin)
Browse organic gemstone (fossilized resin) specimens identified by the Rock Identifier community.
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Fossilized Coral
Hexagonaria (Rugose coral) / Calcium Carbonate (CaCO3)
fossil
Fossilized Coral
Rugosa / Tabulata coral fossils replaced by silica (Chalcedony/Quartz)
fossil
Fossilized Bryozoan
Phylum Bryozoa
fossil
Fossilized Bryozoan
Bryozoa
fossil
Fossilized Coral
Scleractinia (Agatized or Calcite replaced)
fossil
Fossilized Brachiopod
Brachiopoda (Phylum), likely Order Spiriferida or Rhynchonellida
fossil
Fossilized Brachiopod
Phylum Brachiopoda (Calcium Carbonate/Silica replacement)
sedimentary
Fossilized Brachiopod
Brachiopoda (Class Rhynchonellata or Spiriferida)
sedimentary
Fossilized Brachiopod
Brachiopoda (e.g., Rhynchonellida or Spiriferida)
sedimentary
Green Chert
Microcrystalline Quartz (SiO2)
sedimentary
Petoskey Stone
Hexagonaria percarinata
fossil
Petoskey Stone (Fossilized Coral)
Hexagonaria percarinata
sedimentary
Coprolite
Coprolite
sedimentary
Fossiliferous Limestone with Crinoid stems
Limestone (CaCO3) containing Crinoidea fossils
sedimentary
Dark volcanic sand / basaltic sand
Basalt-derived lithic sand, chiefly plagioclase, pyroxene, and volcanic glass
igneous
Petoskey Stone
Hexagonaria percarinata (Fossilized Rugose Coral)
sedimentary
Sea Urchin Fossil
Echinoidea (test/fossil)
fossil
Coral Fossil / Coral Fragment
Scleractinia / Calcium Carbonate (CaCO3)
fossil
Sandstone Pebble
Arenite (SiO2 with minor mineral cements)
sedimentary
Petoskey Stone (Fossilized Rugose Coral)
Hexagonaria percarinata
sedimentary
Fossilized Bone Chunk (likely Dinosaur or Large Mammal)
Permineralized Fossil Bone
sedimentary
Sandstone
Arenite (SiO2 primarily)
sedimentary
Sandstone (Ferruginous)
Arenite with Iron Oxide staining (Fe2O3)
sedimentary
Sandstone Concretion
Clastic sedimentary rock (primarily Silica, SiO2, or Calcium Carbonate, CaCO3)
sedimentary
Sandstone
Clastic Sedimentary Rock (composed of SiO2 grains)
sedimentary
Sandstone
Arenite (SiO2 principal)
sedimentary
Polished agate geode slice
Microcrystalline quartz (chalcedony), SiO₂, with iron-oxide coloration
mineral
Gastropod Fossil
Phylum Mollusca, Class Gastropoda (Calcium Carbonate, CaCO3)
sedimentary
Moss Agate
Silicon Dioxide (Chalcedony variety) with green hornblende or chlorite inclusions - SiO2
gemstone
Green Jasper
Microcrystalline Quartz (SiO2) with mineral inclusions
sedimentary
Fossilized Brachiopod Shell Fragment
Brachiopoda (Class: Rhynchonellata or Strophomenata)
fossil
Crinoid Fossil Limestone
Crinoidal Limestone (Calcite / CaCO3)
sedimentary
Tumbled yellow chalcedony (likely citrine or yellow jasper)
Microcrystalline quartz, SiO₂; exact identification is uncertain from the photograph
mineral
Shiva Eye Shell Fossil (Operculum)
Turbo marmoratus (Operculum)
fossil
Engineered Quartz (Quartzite look-alike)
Silicon Dioxide (SiO2) composite
mineral-based composite
Kambaba Jasper (Crocodile Jasper)
Fossilized Stromatolite (Cyanobacteria microfossils in silica Matrix)
sedimentary
Seashell Fragment
Calcium Carbonate (CaCO3) in the form of Aragonite or Calcite
mineral
Pink Opal
Hydrated silica (SiO2 "n H2O)
mineral
Cockle Shell Fossil
Cardium (Bivalvia)
fossil
Geode / Fossilized Gastropod or Shell Cast
Silicon dioxide (Quartz) replacement / fossil mold
sedimentary
Sandstone (Limonitic/Arkose)
Sandstone (primarily SiO2 with FeO(OH)·nH2O)
sedimentary