Shell Cameo
Cypraecassis rufa (Bullmouth Queen Helmet Shell)
mineraloid / biogenic specimen
Category
Biogenic Material
Browse biogenic material specimens identified by the Rock Identifier community.
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Pearl
Biogenic Calcium Carbonate (Aragonite/Calcite), CaCO3
mineral
Pearl
Aragonite / Calcium Carbonate (CaCO3)
mineral
Chert (Flint)
Microcrystalline or cryptocrystalline quartz (SiO2)
sedimentary
Pearl
Aragonite and Calcite (CaCO3) with Conchiolin
mineral
Calcite
Calcium Carbonate (CaCO3)
mineral
Chert / Flint
Microcrystalline Quartz (SiO2)
sedimentary
Operculum shell (often called "Shiva's Eye" or "Cat's Eye")
Operculum of a gastropod (e.g., Turbinidae family), primarily Calcium Carbonate (CaCO3) in the form of aragonite.
fossil
Likely coral fragment or porous limestone
Calcareous biogenic carbonate, primarily calcite (CaCO₃); exact identification is uncertain from the image
sedimentary
Fossiliferous Limestone (with Rugose Coral)
Limestone with Tetracoralla (Rugosa) fossil
fossil
Beach Pebbles and Quartz Aggregates
Quartz pebbles and biogenic fragments (SiO2, CaCO3)
sedimentary
Fossiliferous Limestone
Biogenic Sedimentary Rock (Calcium Carbonate, CaCO3)
sedimentary
Fossiliferous Limestone
Calcium Carbonate (CaCO3) matrix with biogenic fragments
fossil
Fossiliferous Limestone
Biogenic Sedimentary Rock (Calcium Carbonate, CaCO3)
sedimentary
Fossiliferous Limestone
Biogenic Sedimentary Rock / CaCO3 with fossil fragments
sedimentary
Bay Scallop Shell
Argopecten irradians (Biogenic Calcium Carbonate / CaCO3)
sedimentary
Atlantic Calico Scallop (Biogenic Aragonite/Calcite)
Argopecten gibbus (Chemical: CaCO3)
mineral
Mother of Pearl (Nacre)
Nacre (Aragonite/Conchiolin), CaCO3 + Organic Polymers
mineral
Banded Chert / Agate
Silicon Dioxide (SiO2)
sedimentary
Chert (Iron-stained)
Microcrystalline or cryptocrystalline Quartz (SiO2)
sedimentary
Calcite in Matrix
Calcium Carbonate (CaCO3)
mineral
Fossiliferous Limestone
Fossiliferous Limestone (CaCO3)
sedimentary
Kidney Stone (Urolith / Calcium Oxalate Stone)
Calcium Oxalate Monohydrate (Whewellite) / Calcium Oxalate Dihydrate (Weddellite)
mineral
Flint or chert fragment
Microcrystalline quartz (SiO₂), likely flint/chert
sedimentary
Sand dollar fossil
Clypeasteroida (echinoid test), commonly Clypeasteroides spp.
fossil
Black Pearl (Tahitian-style Cultured Pearl)
Calcium Carbonate (Aragonite) with Conchiolin (CaCO3)
mineral
Chert (Flint / Jasper / Hornstone)
Microcrystalline Quartz (SiO2)
sedimentary
Green Chert (Jasper / Flint)
Silicon Dioxide (SiO2)
sedimentary
Oyster Shell (Biogenic Calcium Carbonate)
Crassostrea virginica (or related species) - Calcium Carbonate (CaCO3)
sedimentary
Flint or chert
Microcrystalline quartz (SiO₂), likely gray chert/flint
sedimentary
Cat's Eye Shell (Shiva Shell)
Operculum of the Turbo petholatus (Tapestry Turban Snail), predominantly Calcium Carbonate (Aragonite)
mineraloid / biogenic specimen
Chert Pebble with Quartz Veining
Microcrystalline Quartz (SiO2)
sedimentary
Fossiliferous Limestone
CaCO3 (principally Calcite or Aragonite)
sedimentary
Flint or chert fragment
Microcrystalline quartz (SiO₂), typically chalcedony with possible impurities
sedimentary
Shell Cameo (Sardonyx Shell)
Cassis madagascariensis (Sardonyx shell)
mineral (biogenic silica/calcium carbonate substrate)
Spondylus Oyster Calcification / Fossilized Oyster
Spondylus (Thorny Oyster) / Calcium Carbonate (CaCO3)
sedimentary
Pearl
Biogenic Calcium Carbonate (Aragonite and Conchiolin), CaCO3
mineral
Tahitian Pearl
Biogenic Calcium Carbonate (Aragonite/Calcite), CaCO3
mineral
Fossiliferous Limestone
Biogenic Limestone containing marine invertebrate fossils
sedimentary
Fossiliferous Limestone
Biogenic Sedimentary Rock (Calcium Carbonate, CaCO3)
sedimentary
Fossiliferous Limestone (or Bryozoan/Coral Fossil Pebble)
Biogenic Sedimentary Rock (Calcium Carbonate, CaCO3)
sedimentary
Fossiliferous Limestone
Biogenic Sedimentary Rock (Calcium Carbonate with Fossils)
sedimentary