Rock Identifier

Category

Mineral (Biogenic Replacement)

Browse mineral (biogenic replacement) specimens identified by the Rock Identifier community.

Fossilized bivalve shell (Recrystallized calcium-carbonate shell, commonly fossil oyster or clam (Bivalvia)) — fossil

Fossilized bivalve shell

Recrystallized calcium-carbonate shell, commonly fossil oyster or clam (Bivalvia)

Fossil bivalve shell (Likely a fossilized oyster or other marine bivalve; exact genus is indeterminate from the image) — fossil

Fossil bivalve shell

Likely a fossilized oyster or other marine bivalve; exact genus is indeterminate from the image

Hematite / Jasper (Iron(III) oxide (Fe2O3) in Quartz (SiO2)) — mineral / sedimentary

Hematite / Jasper

Iron(III) oxide (Fe2O3) in Quartz (SiO2)

mineral / sedimentary

Polished red jasper (Jasper, an opaque microcrystalline variety of quartz (SiO₂), colored mainly by iron oxides) — mineral

Polished red jasper

Jasper, an opaque microcrystalline variety of quartz (SiO₂), colored mainly by iron oxides

Galena (Galena (lead sulfide, PbS)) — mineral

Galena

Galena (lead sulfide, PbS)

Silver-gray metallic ore, possibly galena-bearing rock (Likely galena (PbS) in a host rock, but identification is uncertain from the photograph) — mineral

Silver-gray metallic ore, possibly galena-bearing rock

Likely galena (PbS) in a host rock, but identification is uncertain from the photograph

Carnelian (Red Chalcedony) (Silicon Dioxide (SiO2) with iron oxide impurities) — mineral

Carnelian (Red Chalcedony)

Silicon Dioxide (SiO2) with iron oxide impurities

Sodalite (Sodium Aluminum Silicate Chloride (Na8Al6Si6O24Cl2)) — mineral

Sodalite

Sodium Aluminum Silicate Chloride (Na8Al6Si6O24Cl2)

Silver-bearing galena ore (Galena (PbS), likely in a quartz/carbonate-rich matrix with possible sulfide minerals) — mineral

Silver-bearing galena ore

Galena (PbS), likely in a quartz/carbonate-rich matrix with possible sulfide minerals

Flint (Chert Node) (Silicon Dioxide (SiO2)) — sedimentary

Flint (Chert Node)

Silicon Dioxide (SiO2)

Iron-rich weathered pebble (Likely limonite/goethite-bearing rock; exact identification requires testing) — mineral

Iron-rich weathered pebble

Likely limonite/goethite-bearing rock; exact identification requires testing

Magnetite (Lodestone) (Magnetite (Fe3O4)) — mineral

Magnetite (Lodestone)

Magnetite (Fe3O4)

Limonite-goethite ironstone specimen (Goethite (α-FeO(OH)) with limonite, quartz, and iron oxides) — mineral

Limonite-goethite ironstone specimen

Goethite (α-FeO(OH)) with limonite, quartz, and iron oxides

Tumbled brown jasper (Microcrystalline quartz (chalcedony), chiefly SiO₂, colored by iron oxides and other inclusions) — mineral

Tumbled brown jasper

Microcrystalline quartz (chalcedony), chiefly SiO₂, colored by iron oxides and other inclusions

Petrified Wood (Silicified wood (primarily SiO2 - Silicon Dioxide)) — mineral

Petrified Wood

Silicified wood (primarily SiO2 - Silicon Dioxide)

Magnetite (Magnetite (Iron(II,III) oxide, Fe3O4)) — mineral

Magnetite

Magnetite (Iron(II,III) oxide, Fe3O4)

Likely raw galena fragment (Galena (lead sulfide, PbS), possibly with metallic sulfide matrix) — mineral

Likely raw galena fragment

Galena (lead sulfide, PbS), possibly with metallic sulfide matrix

Tiger's Eye (Pseudomorph of Quartz after Crocidolite (SiO2)) — mineral

Tiger's Eye

Pseudomorph of Quartz after Crocidolite (SiO2)

Galena (likely) (Galena, lead sulfide (PbS)) — mineral

Galena (likely)

Galena, lead sulfide (PbS)

Black Jasper (Etched) (Silicon Dioxide (SiO2) with impurities) — mineral

Black Jasper (Etched)

Silicon Dioxide (SiO2) with impurities

Chalcedony (Cryptocrystalline Quartz (SiO2)) — mineral

Chalcedony

Cryptocrystalline Quartz (SiO2)

Chert (Jasper) (Microcrystalline Quartz (SiO2)) — sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

Limonite-stained Chert (Microcrystalline Quartz (SiO2) with Goethite/Limonite (FeO(OH)·nH2O)) — sedimentary

Limonite-stained Chert

Microcrystalline Quartz (SiO2) with Goethite/Limonite (FeO(OH)·nH2O)

Chalcedony (possibly agate or common quartz) (Microcrystalline quartz, SiO₂) — mineral

Chalcedony (possibly agate or common quartz)

Microcrystalline quartz, SiO₂

Tumbled Tiger's Eye (Silicon dioxide with crocidolite inclusions (SiO2)) — mineral

Tumbled Tiger's Eye

Silicon dioxide with crocidolite inclusions (SiO2)

Chert Nodule (Microcrystalline Quartz (SiO2)) — sedimentary

Chert Nodule

Microcrystalline Quartz (SiO2)

Chert (Common Opal variant) (Silicon Dioxide (SiO2)) — sedimentary

Chert (Common Opal variant)

Silicon Dioxide (SiO2)

Chert (Green Chert/Jasper) (Chert (primarily Microcrystalline Quartz, SiO2)) — sedimentary

Chert (Green Chert/Jasper)

Chert (primarily Microcrystalline Quartz, SiO2)

Chert (specifically Flint) (Microcrystalline or cryptocrystalline Quartz (SiO2)) — sedimentary

Chert (specifically Flint)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Favosites Fossil (Honeycomb Coral) (Favosites (Extinct genus of Tabulate Coral)) — sedimentary

Favosites Fossil (Honeycomb Coral)

Favosites (Extinct genus of Tabulate Coral)

Ammonite fossil (Fossilized ammonoid cephalopod; likely an involute ammonite, exact genus/species indeterminate) — fossil

Ammonite fossil

Fossilized ammonoid cephalopod; likely an involute ammonite, exact genus/species indeterminate

Fossilized ammonite fragment (Ammonoidea; commonly Jurassic or Cretaceous ammonite, preserved mainly as calcite) — fossil

Fossilized ammonite fragment

Ammonoidea; commonly Jurassic or Cretaceous ammonite, preserved mainly as calcite

Jasper (Banded Argillite/Chert mix) (Silicon Dioxide (SiO2) with iron oxide inclusions) — sedimentary

Jasper (Banded Argillite/Chert mix)

Silicon Dioxide (SiO2) with iron oxide inclusions

Agatized Dinosaur Bone (Permineralized Dinosaur Bone (Silicified/Agatized Bone)) — fossil

Agatized Dinosaur Bone

Permineralized Dinosaur Bone (Silicified/Agatized Bone)

Ammonite Fossil (Ammonoidea) — fossil

Ammonite Fossil

Ammonoidea

Jasper or Agate (Chalcedony) (Silicon Dioxide (SiO2) with impurities) — sedimentary

Jasper or Agate (Chalcedony)

Silicon Dioxide (SiO2) with impurities

Tiger's Eye (Pseudomorph of Quartz after Crocidolite (SiO2)) — metamorphic

Tiger's Eye

Pseudomorph of Quartz after Crocidolite (SiO2)

Chert (with Patina) (Microcrystalline Quartz (SiO2)) — sedimentary

Chert (with Patina)

Microcrystalline Quartz (SiO2)

Tumbled yellow jasper (likely serpentine or calcite-rich stone) (Jasper: microcrystalline quartz (SiO₂); exact yellow veining may indicate serpentine, calcite, or iron oxides) — mineral

Tumbled yellow jasper (likely serpentine or calcite-rich stone)

Jasper: microcrystalline quartz (SiO₂); exact yellow veining may indicate serpentine, calcite, or iron oxides

Tumbled fossil shark tooth pendant (Likely fossilized shark tooth, possibly Otodus or Carcharhinus; exact species cannot be confirmed from the image) — fossil

Tumbled fossil shark tooth pendant

Likely fossilized shark tooth, possibly Otodus or Carcharhinus; exact species cannot be confirmed from the image

Chert (Green Chert or Jasper) (Silicon Dioxide (SiO2)) — sedimentary

Chert (Green Chert or Jasper)

Silicon Dioxide (SiO2)

Chert (Jasper variety) (Silicon Dioxide (SiO2)) — sedimentary

Chert (Jasper variety)

Silicon Dioxide (SiO2)