Rock Identifier

Category

Mineral (Biogenic Replacement)

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

Raw green fluorite (probable) (Fluorite, calcium fluoride (CaF₂)) — mineral

Raw green fluorite (probable)

Fluorite, calcium fluoride (CaF₂)

mineral
Tiger's Eye (Rough Slab) (Pseudomorph of Quartz after Crocidolite (SiO2 with Fe-containing inclusions)) — mineral

Tiger's Eye (Rough Slab)

Pseudomorph of Quartz after Crocidolite (SiO2 with Fe-containing inclusions)

mineral
Chalcedony (specifically Agate or Water-worn Quartzite) (Silicon Dioxide (SiO2)) — mineral

Chalcedony (specifically Agate or Water-worn Quartzite)

Silicon Dioxide (SiO2)

mineral
Petrified Coral (Agatized Coral) (Fossilized Anthozoa (Silicon Dioxide replacement - SiO2)) — fossil

Petrified Coral (Agatized Coral)

Fossilized Anthozoa (Silicon Dioxide replacement - SiO2)

fossil
Petrified Wood (Silicified wood (SiO2 - Silicon Dioxide)) — sedimentary

Petrified Wood

Silicified wood (SiO2 - Silicon Dioxide)

sedimentary
Fossil Coral (Petoskey Stone or Chain Coral Pebble) (Hexagonaria percarinata / Rugosa coral (CaCO3)) — fossil

Fossil Coral (Petoskey Stone or Chain Coral Pebble)

Hexagonaria percarinata / Rugosa coral (CaCO3)

fossil
Geode / Fossilized Gastropod or Shell Cast (Silicon dioxide (Quartz) replacement / fossil mold) — sedimentary

Geode / Fossilized Gastropod or Shell Cast

Silicon dioxide (Quartz) replacement / fossil mold

sedimentary
Petrified Wood (Silicified Wood (SiO2)) — sedimentary

Petrified Wood

Silicified Wood (SiO2)

sedimentary
Chert / Flint Nodules (Cryptocrystalline Quartz (SiO2)) — sedimentary

Chert / Flint Nodules

Cryptocrystalline Quartz (SiO2)

sedimentary
Chert (Flinty variety) (Microcrystalline Quartz (SiO2)) — sedimentary

Chert (Flinty variety)

Microcrystalline Quartz (SiO2)

sedimentary
Green Banded Chert (Agate/Jasper) (Silicon Dioxide (SiO2) with trace impurities of Chlorite or Glauconite) — sedimentary

Green Banded Chert (Agate/Jasper)

Silicon Dioxide (SiO2) with trace impurities of Chlorite or Glauconite

sedimentary
Yellow Jasper (Silicon Dioxide (SiO2) with goethite or iron oxide inclusions) — sedimentary

Yellow Jasper

Silicon Dioxide (SiO2) with goethite or iron oxide inclusions

sedimentary
Chert (specifically Jasper/Carnelian Agate) (Microcrystalline Quartz (SiO2)) — sedimentary

Chert (specifically Jasper/Carnelian Agate)

Microcrystalline Quartz (SiO2)

sedimentary
Limestone with Chert Nodule (Carbonate rock (CaCO3) with Microcrystalline Silicon Dioxide (SiO2) inclusion) — sedimentary

Limestone with Chert Nodule

Carbonate rock (CaCO3) with Microcrystalline Silicon Dioxide (SiO2) inclusion

sedimentary
Red Jasper (Silicon Dioxide (SiO2) with Hematite impurities) — sedimentary

Red Jasper

Silicon Dioxide (SiO2) with Hematite impurities

sedimentary
Polished dark pebble, possibly basalt or chert (Uncertain; likely fine-grained basalt (plagioclase–pyroxene) or microcrystalline silica (chert)) — igneous

Polished dark pebble, possibly basalt or chert

Uncertain; likely fine-grained basalt (plagioclase–pyroxene) or microcrystalline silica (chert)

igneous
Tiger's Eye (Rough) (Pseudomorph of Quartz after Crocidolite (SiO2 with Iron inclusions)) — Mineral

Tiger's Eye (Rough)

Pseudomorph of Quartz after Crocidolite (SiO2 with Iron inclusions)

Mineral
Chalcedony (specifically Agate or Common Opal variety) (Cryptocrystalline Silica (SiO2)) — mineral

Chalcedony (specifically Agate or Common Opal variety)

Cryptocrystalline Silica (SiO2)

mineral
Petoskey Stone (Hexagonaria percarinata) — fossil

Petoskey Stone

Hexagonaria percarinata

fossil
Chert (often called Flint in this context) (Microcrystalline or Cryptocrystalline Quartz (SiO2)) — sedimentary

Chert (often called Flint in this context)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

sedimentary
Fossil Coral (Fossilized Scleractinia or Tabulata (various genera/species)) — Sedimentary

Fossil Coral

Fossilized Scleractinia or Tabulata (various genera/species)

Sedimentary
Chert (Yellow Jasper/Flint) (Silicon Dioxide (SiO2)) — sedimentary

Chert (Yellow Jasper/Flint)

Silicon Dioxide (SiO2)

sedimentary
Petrified Wood (Silicified Wood (primarily SiO2)) — sedimentary

Petrified Wood

Silicified Wood (primarily SiO2)

sedimentary
Fossilized Brachiopod (Phylum Brachiopoda (General mineral composition: Calcite/CaCO₃ or Silica/SiO₂)) — sedimentary

Fossilized Brachiopod

Phylum Brachiopoda (General mineral composition: Calcite/CaCO₃ or Silica/SiO₂)

sedimentary
Jasper (Silicon Dioxide (SiO2)) — mineral

Jasper

Silicon Dioxide (SiO2)

mineral
Chert (Chert / Flint) (Silicon Dioxide (SiO2)) — sedimentary

Chert (Chert / Flint)

Silicon Dioxide (SiO2)

sedimentary
Petrified Wood (Silicified Wood (primarily SiO2)) — sedimentary

Petrified Wood

Silicified Wood (primarily SiO2)

sedimentary
Flint (or Chert) (Microcrystalline quartz (SiO2)) — sedimentary

Flint (or Chert)

Microcrystalline quartz (SiO2)

sedimentary
Chert (Jasper/Flint variety) (Microcrystalline Quartz (SiO2)) — sedimentary

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

sedimentary
Fossil Coral (Rugose or Tabulate Coral Fossil (CaCO3 replacement)) — fossil

Fossil Coral

Rugose or Tabulate Coral Fossil (CaCO3 replacement)

fossil
Chert (Chert (Microcrystalline Quartz, SiO2)) — sedimentary

Chert

Chert (Microcrystalline Quartz, SiO2)

sedimentary
Chert (and Petrified Wood) (Silicon Dioxide (SiO2)) — sedimentary

Chert (and Petrified Wood)

Silicon Dioxide (SiO2)

sedimentary
Dinosaur Bone (Petrified/Agatized) (Permineralized Dinosauria Bone (Silicate Replacement)) — fossil

Dinosaur Bone (Petrified/Agatized)

Permineralized Dinosauria Bone (Silicate Replacement)

fossil
Petrified Wood (Silicified wood / Permineralized wood (SiO2)) — fossil

Petrified Wood

Silicified wood / Permineralized wood (SiO2)

fossil
Yellow Chert (Gold-colored River Pebble) (Microcrystalline Quartz (SiO2) with Limonite/Goethite staining) — sedimentary

Yellow Chert (Gold-colored River Pebble)

Microcrystalline Quartz (SiO2) with Limonite/Goethite staining

sedimentary
Petrified Wood (Silicified Wood (SiO2)) — fossil

Petrified Wood

Silicified Wood (SiO2)

fossil
Chert (Flint) (Microcrystalline Quartz (SiO2)) — sedimentary

Chert (Flint)

Microcrystalline Quartz (SiO2)

sedimentary
Petrified Wood (Silicified Wood (primarily SiO2)) — fossil

Petrified Wood

Silicified Wood (primarily SiO2)

fossil
Fossil-bearing ironstone or weathered concretion (Indeterminate; likely ferruginous sandstone/concretion containing a partial fossil impression) — fossil

Fossil-bearing ironstone or weathered concretion

Indeterminate; likely ferruginous sandstone/concretion containing a partial fossil impression

fossil
Petrified Wood (Silicon Dioxide (SiO2) permineralized organic matter) — sedimentary

Petrified Wood

Silicon Dioxide (SiO2) permineralized organic matter

sedimentary
Fossil Coral (Hexagonaria (Rugose coral) / Rugosa) — fossil

Fossil Coral

Hexagonaria (Rugose coral) / Rugosa

fossil
Fossilized Coral (Petoskey Stone type) (Hexagonaria percarinata (Fossilized Rugose Coral)) — sedimentary

Fossilized Coral (Petoskey Stone type)

Hexagonaria percarinata (Fossilized Rugose Coral)

sedimentary