Sedimentary (Biogenic)

Pearl

Calcium Carbonate (CaCO3) in the form of Aragonite

Weathered fossiliferous limestone, likely coral or shell fragment

Calcite (CaCO₃), biogenic limestone; exact fossil taxon indeterminate from the image

Black Pearl (Tahitian Type)

Aragonite / Conchiolin composite (CaCO3)

Pearl

Aragonite (CaCO3) with Conchiolin

Fossil Shark Tooth

Otodus sp. (possibly Otodus obliquus)

Mother of Pearl (Nacre)

Aragonite (layered with organic polymers), CaCO3

Kidney Stone (Calcium Oxalate / Uric Acid)

Calcium Oxalate Monohydrate (Whewellite) / Calcium Oxalate Dihydrate (Weddellite)

Shiva Eye Shell (Operculum)

Calcium Carbonate (Aragonite), CaCO3

Red Coral (Precious Coral)

Corallium rubrum (Calcium Carbonate, CaCO3)

Ammolite

Ammolite (Biogenic Aragonite with trace elements; fossils of Placenticeras meeki and Placenticeras intercalare)

Polished fossil shell or bone fragment (tentative)

Indeterminate biogenic carbonate or fossilized bone; possibly a small gastropod/bivalve fragment

Fossil gastropod shell

Calcareous mollusk shell, chiefly aragonite or calcite (likely a large marine gastropod)

Marine gastropod shell

Calcareous mollusk shell, primarily aragonite (CaCO₃), likely a whelk or conch

Shell Cameo

Cypraecassis rufa (Bullmouth Queen Helmet Shell)

Fossilized Shell Fragment / Mother of Pearl

Calcium Carbonate (CaCO3) - Aragonite/Calcite biomineral

Pearl

Calcium carbonate (CaCO3) + organic conchiolin (Biogenic Mineral)

Pearl

Biogenic Calcium Carbonate (Aragonite/Calcite), CaCO3

Pearl

Aragonite / Calcium Carbonate (CaCO3)

Pearl

Aragonite and Calcite (CaCO3) with Conchiolin

Pearl

Calcium Carbonate (primarily Aragonite and Calcite), CaCO3

Pearl (in a decorative hair comb setting)

Calcium carbonate (CaCO3) primarily as Aragonite, bonded with Conchiolin

Tumbled coral limestone

Biogenic calcarenite/coral limestone, predominantly calcium carbonate (CaCO₃; calcite/aragonite)

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.

Fossiliferous Limestone (with Rugose Coral)

Limestone with Tetracoralla (Rugosa) fossil

Chert

Chert (microcrystalline quartz, SiO2)

Weathered fossil shell fragment

Likely a bivalve or gastropod shell, composed mainly of biogenic calcite/aragonite (CaCO₃)

Pearl (in Marcasite Jewelry)

Biogenic Calcium Carbonate (primarily Aragonite, CaCO3)

Nacre (Mother of Pearl)

Nacre (Biogenic Aragonite/Calcite composite, CaCO3)

Mother of Pearl (Nacre)

Nacre (Aragonite/Conchiolin), CaCO3 + Organic Polymers

Sand dollar fossil

Clypeasteroida (echinoid test), commonly Clypeasteroides spp.

Black Pearl (Tahitian-style Cultured Pearl)

Calcium Carbonate (Aragonite) with Conchiolin (CaCO3)

Beaded mineral/crystal jewelry (likely turquoise and coral accents)

Variable; blue beads may be turquoise (CuAl6(PO4)4(OH)8·4H2O), with possible dyed howlite, glass, or composite materials

Atlantic Calico Scallop (Biogenic Aragonite/Calcite)

Argopecten gibbus (Chemical: CaCO3)

Likely coral fragment or porous limestone

Calcareous biogenic carbonate, primarily calcite (CaCO₃); exact identification is uncertain from the image

Kidney Stone (Urolith / Calcium Oxalate Stone)

Calcium Oxalate Monohydrate (Whewellite) / Calcium Oxalate Dihydrate (Weddellite)

Pearl

Biogenic Calcium Carbonate (Aragonite and Conchiolin), CaCO3

Tahitian Pearl

Biogenic Calcium Carbonate (Aragonite/Calcite), CaCO3

Fossiliferous Limestone / Fossil Fragment

Calcium Carbonate (CaCO3) with indeterminate biogenic remains

Black Freshwater Pearls

Biogenic Calcium Carbonate (Aragonite/Calcite), CaCO3

Shell Cameo (Sardonyx Shell)

Cassis madagascariensis (Sardonyx shell)

Cat's Eye Shell (Shiva Shell)

Operculum of the Turbo petholatus (Tapestry Turban Snail), predominantly Calcium Carbonate (Aragonite)

Fossiliferous limestone pebble (probable coral or shell fossil)

Calcite (CaCO₃), commonly biogenic limestone; exact fossil taxon indeterminate from the image