Fossil Belemnite Guard
Belemnitella spp. (rostrum)
fossil
Category
Sedimentary (With Some Aspects Of Mineral Replacement)
Browse sedimentary (with some aspects of mineral replacement) specimens identified by the Rock Identifier community.
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Ironstone concretion
Siderite or Limonite concretion (FeCO3 or FeO(OH)·nH2O)
sedimentary
Likely fossilized bone or tooth fragment
Indeterminate fossil bone; mineral replacement commonly calcite, silica, or iron oxides
fossil
Ironstone Concretion
Siderite or Hematite Concretion
sedimentary
Pyrite on quartz matrix
Pyrite (FeS₂), likely with quartz (SiO₂) and possibly calcite or clay matrix
mineral
Galena
Galena (lead sulfide, PbS)
mineral
Pyrite in Quartz
FeS2 (Iron Pyrite) with SiO2 (Quartz)
Mineral/Igneous/Hydrothermal
Chert Nodule
Microcrystalline Quartz (SiO2)
sedimentary
Coprolite
Coprolite (fossilized feces)
sedimentary
Chert (or Flint)
Silicon dioxide (SiO2)
sedimentary
Geode with Quartz Crystals
SiO2 (Silicon Dioxide) in a geode formation
Sedimentary/Igneous (depending on host rock)
Fossilized shell or coral fragment
Likely silicified or calcitic marine invertebrate fossil; exact taxon indeterminate from the image
fossil
Kambaba Jasper
Stromatolite Jasper (Microcrystalline Quartz)
sedimentary
Quartz Geode
Silicon Dioxide (SiO2) in Calcareous or Siliceous Matrix
mineral
Chert (within Limestone)
Silicon Dioxide (SiO2) in Calcium Carbonate (CaCO3) matrix
sedimentary
Fossil bivalve shell
Fossilized or calcitic bivalve, likely a scallop-type pectinid (Bivalvia: Pectinidae)
fossil
Fossil Crab
Decapoda (likely Avitelmessus or Raninidae family)
sedimentary
Sandstone (Pebble)
Sandstone (SiO2 with iron oxide impurities)
sedimentary
Quartz Geode Fragment
Silicon Dioxide (SiO2)
mineral
Weathered chert or siliceous limestone
Microcrystalline quartz (SiO₂), possibly with carbonate minerals
sedimentary
Fossil bivalve shell
Likely a fossilized oyster or other marine bivalve; exact genus is indeterminate from the image
fossil
Magnetite (Lodestone)
Magnetite (Fe3O4)
mineral
Silicified Snail Fossil
Gastropod (likely replaced by Chalcedony/Quartz - SiO2)
fossil
Fossilized Echinoid (Sea Urchin)
Echinoidea (Fossil)
sedimentary
Dark rounded pebble, likely hematite-rich ironstone
Possibly hematite (Fe₂O₃) or iron-rich goethite/limonite; the photo alone cannot confirm composition
mineral
Fossilized bone
Petrified bone; commonly fossil vertebrate bone composed largely of hydroxyapatite and silica/calcite replacement minerals
fossil
Chert with Chalcedony/Quartz Vug
Cryptocrystalline Silica (SiO2)
sedimentary
Quartz Geode
Silicon Dioxide (SiO2)
mineral
Fossilized bone fragment
Fossil bone, composed chiefly of carbonate-fluorapatite (bioapatite)
fossil
Green Chert
Silicon Dioxide (SiO2)
sedimentary
Ironstone (Limonite/Hematite concretion)
Ferruginous Siltstone / Goethite (FeO(OH))
sedimentary
Gneiss
Gneiss
metamorphic
Fluorite (translucent octahedral crystal)
Calcium fluoride (CaF2)
mineral
Jasper (Banded Argillite/Chert mix)
Silicon Dioxide (SiO2) with iron oxide inclusions
sedimentary
Moqui Marble (Shaman Stone)
Iron Oxide Concretion (Goethite/Hematite shell with Sandstone core)
sedimentary
Tooth fossil, likely mammalian or reptilian fragment
Indeterminate fossilized tooth; enamel and dentine, taxon unresolved
fossil
Fossil Shark Tooth
Selachii fossil
fossil
Jasper or Agate (Chalcedony)
Silicon Dioxide (SiO2) with impurities
sedimentary
Sandstone
Arenite (SiO2 principal component)
sedimentary
Gneiss
Gneiss (High-grade metamorphic rock)
metamorphic
Pyrite (Fool's Gold)
Iron Disulfide (FeS2)
mineral
Iron Concretion
Ferruginous concretion (Fe2O3·nH2O / FeO(OH))
sedimentary