Sedimentary (Biogenic)

Fossiliferous Limestone / Fossil Fragment

Calcium Carbonate Matrix with Biogenic Inclusions (CaCO3)

Tumbled yellow-brown stone, likely chert or jasper

Microcrystalline quartz (SiO₂), possibly iron-stained chert/jasper

Chert (Nodule)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Flint or chert

Microcrystalline quartz (SiO₂), likely gray chert/flint

Likely weathered chert or siliceous shale

Cryptocrystalline quartz (SiO₂), possibly with clay minerals

Chert or flint fragment

Microcrystalline quartz (SiO₂), possibly iron-stained chert

Chert Pebble with Quartz Veining

Microcrystalline Quartz (SiO2)

Cultured freshwater pearls

Pearl; primarily aragonite (CaCO₃) in nacre with an organic conchiolin matrix

Coquina

Biogenic Limestone (Calcite/Aragonite base, CaCO3)

Fossiliferous Limestone

CaCO3 (principally Calcite or Aragonite)

Flint or chert fragment

Microcrystalline quartz (SiO₂), typically chalcedony with possible impurities

Banded chert or flint

Microcrystalline quartz (SiO₂), likely with iron-oxide and dark organic/mineral impurities

Chert

Chert (Microcrystalline Quartz, SiO2)

Precious Coral

Corallium rubrum (Calcium Carbonate, CaCO3)

Pearl (Biogenic Mineraloid)

Calcium carbonate (CaCO3) primarily as Aragonite

Tumbled brown chert (likely flint)

Microcrystalline quartz/chalcedony, SiO₂

Hag Stone (Holey Rock / Fossiliferous Limestone)

Limestone (CaCO3) with natural erosion / fossil cavities

Weathered chert or flint pebble

Microcrystalline quartz (SiO₂), likely chert/flint with possible carbonate or quartz vein

Chalk

CaCO3 (primarily Calcium Carbonate), biogenic sedimentary rock

Brown flint or chert pebble

Microcrystalline quartz (SiO₂), commonly with iron-oxide staining

Yellow-brown chert or silicified rock fragment

Microcrystalline quartz (SiO₂), likely chert or chalcedony-rich material

Chert (and associated Flint)

Silicon Dioxide (SiO2)

Likely fossilized shell or carbonate concretion

Indeterminate biogenic calcium carbonate, commonly calcite (CaCO₃)

Red Coral (Precious Coral)

Corallium rubrum (calcium carbonate, primarily calcite with trace carotenes)

Land Snail Shell

Gastropoda (Calcium Carbonate, CaCO3)

Pearl

Calcium carbonate (CaCO3) as Aragonite or Calcite

Freshwater Pearl

Calcium Carbonate (CaCO3) - Aragonite/Calcite organic composite

Pearl

Calcium carbonate (CaCO3) - mainly Aragonite with Conchiolin

Possible fossilized shell or coral fragment

Indeterminate biogenic carbonate, likely calcite (CaCO₃)

Pearl

Calcium carbonate (CaCO3) - Aragonite/Calcite variety

Fossiliferous Limestone (Coquina / Shell Limestone)

Bioclastic Limestone (CaCO3)

Polished brown chert or jasper pebble

Microcrystalline quartz (SiO₂), likely chert/jasper

Weathered chert or siliceous limestone

Microcrystalline quartz (SiO₂), possibly replacing or cementing carbonate rock

Polished dark stone, likely basalt or black jasper

Basalt (fine-grained plagioclase–pyroxene rock), possibly iron-rich jasper/chert

Water and Silt (Sedimentary Environment)

Suspended Sediment / H2O (dihydrogen monoxide)

Flint or chert fragment

Microcrystalline quartz (SiO₂), commonly chalcedony with possible iron-oxide impurities

Ammolite

Biogenic gemstone (Aragonite, CaCO3)

Fossil oyster shell

Fossilized bivalve, likely Ostrea or Crassostrea; calcite (CaCO₃) shell

Chert (Pink/Red variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Tahitian Pearl (Black / Pistachio Pearl)

Biogenic Aragonite / Calcite (CaCO3 with conchiolin)

Mother of Pearl (Nacre)

Calcium Carbonate (Aragonite) with organic conchiolin

Yellow chert or jasper pebble

Microcrystalline quartz (SiO₂), likely iron-oxide-stained chert/jasper