Biogenic Material

Fossiliferous Limestone

Biogenic Sedimentary Rock (Calcium Carbonate, CaCO3)

Stromatolite

Biogenic Sedimentary Rock (Lithified microbial mat)

Chalk (Calcitic)

Calcium Carbonate (CaCO3) - Biogenic Sedimentary Rock

Black Freshwater Pearls

Biogenic Calcium Carbonate (Aragonite/Calcite), CaCO3

Stromatolite

Biogenic Sedimentary Rock (Precambrian Stromatolite fossil)

Stromatolite

Laminated biogenic sedimentary structure (formed by Cyanobacteria)

Hag Stone (Holey Rock / Fossiliferous Limestone)

Limestone (CaCO3) with natural erosion / fossil cavities

Scallop Shell Fossil

Pecten sp.

Pearl

Calcium Carbonate (Aragonite) - CaCO3

Pearl (Imitation or Cultured)

Calcium Carbonate (Aragonite/Calcite) - CaCO3

Chert (Nodule)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Mookaite Jasper

Silicified Radiolarite (SiO2)

Polished dark stone, likely basalt or black jasper

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

Fossilized cylindrical shell or bone fragment

Indeterminate biogenic carbonate or phosphatic fossil; possible fragment of a tubular shell (e.g., scaphopod) or hollow bone

Pearl oyster shell with natural pearls

Molluscan shell, likely Pinctada spp.; pearls are aragonite (CaCO₃)

Tumbled brown chert (likely flint)

Microcrystalline quartz/chalcedony, SiO₂

Fossiliferous Limestone (Coquina / Shell Limestone)

Bioclastic Limestone (CaCO3)

Weathered chert or siliceous limestone

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

Weathered chert or flint pebble

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

Pearl

Aragonite (CaCO3) with Conchiolin

Fossil oyster shell

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

Limestone with Calcite Veining

Calcium Carbonate (CaCO3) - Biogenic/Chemical Sedimentary Rock

Pearl necklace

Pearl (biogenic calcium carbonate, chiefly aragonite; CaCO₃)

Fossiliferous Limestone

Biogenic Sedimentary Rock (primarily CaCO3 with fossil fragments)

Tahitian Black Pearl

Biogenic Calcium Carbonate (Aragonite/Conchiolin Mixture), CaCO3

Polished brown chert or jasper pebble

Microcrystalline quartz (SiO₂), likely chert/jasper

Flint (chert), likely a worked or fractured nodule

Microcrystalline quartz/chalcedony (SiO₂)

Tumbled dark stone, possibly chert or basalt

Indeterminate; likely fine-grained basalt (plagioclase–pyroxene) or microcrystalline chert (quartz, SiO₂)

Limestone (Chalk / Calcite Rock)

Calcium Carbonate (CaCO3)

Chalky limestone

Micritic calcite (CaCO₃), likely biogenic limestone/chalk

Layered limestone, likely stromatolitic or microbial limestone

Limestone; predominantly calcite (CaCO₃), possibly biogenic micrite

Jasper containing fossilized inclusions

Silicon Dioxide (SiO2) with trace impurities and biogenic inclusions

Banded chert or siliceous sedimentary rock

Microcrystalline quartz (chalcedony), SiO₂, with iron-oxide staining and possible carbonate/clay layers

Chert (likely jasper-bearing chert)

Microcrystalline quartz (SiO₂), with iron-oxide staining and possible chalcedony

Flint

Chert (a form of cryptocrystalline quartz, chemical formula SiO₂)

Polished brown flint/chert (likely)

Microcrystalline quartz, SiO₂ (chalcedonic flint/chert)

Queen Conch Shell (Biogenic Calcium Carbonate)

Aliger gigas (synonym Strombus gigas); Composition: Aragonite (CaCO3)

Weathered quartz-rich rock, likely chert or quartzite

Quartzite/chert; predominantly microcrystalline quartz (SiO₂), with iron-oxide staining and possible minor feldspar or clay minerals

Calcite

Calcite (Mineral; CaCO₃)

Chert (or Flint)

Chert (cryptocrystalline quartz), SiO2

Calcite

Calcite (Calcium Carbonate, CaCO3)

Sea Shell (Fighting Conch Fragment)

Calcium Carbonate (CaCO3) - Strombus alatus fragment