Coquina
Biogenic Limestone (Calcite/Aragonite base, CaCO3)
sedimentary
Category
Mineral (Biogenic Replacement)
Browse mineral (biogenic replacement) specimens identified by the Rock Identifier community.
Tiger's Eye
Quartz pseudomorph after crocidolite (SiO2)
gemstone
Pyrite
Iron sulfide (FeS2)
mineral
Chert (Smoky Variety)
Microcrystalline Quartz (SiO2)
sedimentary
Pyrite
Iron Disulfide (FeS2)
mineral
Fluorite on Host Rock
Calcium Fluoride (CaF2)
mineral
Pyrite
Iron Pyrite (FeS2)
mineral
Pyrite
Iron Sulfide (FeS2)
mineral
Fossilized Gastropod / Coral
Phylum Mollusca / Cnidaria (Silicified or Calcified)
fossil
Chert (Jasper or Flint variant)
Chert (composed of microcrystalline quartz, SiO2)
sedimentary
Blue Chalcedony
Silicon Dioxide (SiO2)
mineral
Pyrite (Fool's Gold)
Iron Sulfide (FeS2)
mineral
Pearl (in a decorative hair comb setting)
Calcium carbonate (CaCO3) primarily as Aragonite, bonded with Conchiolin
Organic Mineraloid
Tahitian Black Pearl
Biogenic Calcium Carbonate (Aragonite/Conchiolin Mixture), CaCO3
mineral
Fossilized Bone
Permineralized Vertebrate Bone
fossil
Banded chert or flint
Microcrystalline quartz (SiO₂), likely with iron-oxide and dark organic/mineral impurities
sedimentary
Fossil Shell
Invertebrate fossil (Mollusca)
fossil
Tumbled jasper or iron-rich chert
Microcrystalline quartz (SiO₂), likely colored by iron oxides
mineral
Polished brecciated jasper (likely septarian or iron-rich jasper)
Microcrystalline quartz (chalcedony), SiO₂, with iron oxides and possibly calcite or other rock fragments
sedimentary
Ammonite Fossil
Ammonoidea subclass (calcium carbonate / silica replacement)
fossil
Fossilized Shark Tooth (Otodus)
Otodus obliquus
fossil
Fossilized Shark Tooth
Elasmobranchii (various species, possibly Carcharias or Odontaspis)
fossil
Bay Scallop Shell
Argopecten irradians (Biogenic Calcium Carbonate / CaCO3)
sedimentary
Chert
Silicon dioxide (SiO2)
sedimentary
Rhodonite
Manganese Inosilicate (Mn,Fe,Mg,Ca)SiO3
mineral
Magnetite / Lodestone
Magnetite (Fe3O4)
mineral
Baryte (Barite)
Barium sulfate (BaSO4)
mineral
Petrified wood
Silicified fossil wood, commonly quartz/chalcedony (SiO₂) replacing woody tissue
fossil
Tumbled jasper
Microcrystalline quartz (SiO₂), commonly iron-oxide-bearing chalcedony
mineral
Pyrite (Fool's Gold)
Iron Sulfide (FeS2)
mineral
Fluorite
Calcium Fluoride (CaF2)
mineral
Jasper
SiO2 (Cryptocrystalline quartz)
mineral
Worn quartz-rich pebble
Likely microcrystalline quartz (SiO₂), possibly a weathered chert or milky quartz fragment
mineral
Polished orbicular jasper (likely ocean jasper)
Silicified volcanic rock; microcrystalline quartz/chalcedony (SiO₂) with iron oxides and altered volcanic minerals
metamorphic
Polished brown jasper (likely brecciated or orbicular jasper)
Microcrystalline quartz/chalcedony, SiO₂, colored by iron oxides and other inclusions
mineral
Pyrite (on host rock)
Iron Sulfide (FeS2)
mineral
Green Chert (Jasper / Flint)
Silicon Dioxide (SiO2)
sedimentary
Galena
Lead Sulfide (PbS)
mineral
Shell Cameo (Sardonyx Shell)
Cassis madagascariensis (Sardonyx shell)
mineral (biogenic silica/calcium carbonate substrate)
Fossil Shark Tooth
Lamniformes (order) - likely Cretalamna or Carcharias species
fossil
Fossilized Dinosaur Skull (Tyrannosaurus rex)
Tyrannosaurus rex (permineralized fossil), rich in Hydroxylapatite/Silica
sedimentary
Dinosaur Fossil (Tyrannosaurus rex skull replica/specimen)
Tyrannosaurus rex (fossilized in permineralized sedimentary matrix)
sedimentary