Limestone

Fossiliferous limestone

Bioclastic carbonate rock, chiefly calcite (CaCO₃), containing a likely colonial coral or bryozoan fossil

Crinoid Stem Fossil

Class Crinoidea (Echinodermata)

Geode

Quartz nodule / Chalcedony-lined cavity

Fossilized Ripple Marks or Stromatolite

Sedimentary ripple mark imprint / Biosedimentary structure

Chert (or Fossiliferous Limestone)

Microcrystalline Quartz (SiO2) / Calcium Carbonate (CaCO3)

Septarian (Dragon Stone)

Septarian Concretion (SiO2 + CaCO3)

Hag Stone (Piddock bored rock)

Calcareous sedimentary rock featuring Pholadidae borings

Fossilized Gastropod Internal Mold

Steinkern (Mollusca: Gastropoda)

Chert or Flint

Silicon dioxide (SiO2)

Yellow Calcite

Calcium Carbonate, CaCO3

Pyrite Nodule

Iron Sulfide (FeS2)

Galena

Lead Sulfide (PbS)

Flint / Chert

Microcrystalline quartz (SiO2)

Celestite

Celestine (SrSO4)

Yellow Calcite (Polished Pebble)

Calcium Carbonate (CaCO3)

Calcite

Calcium Carbonate (CaCO3)

Blue Apatite

Apatite-(CaF), Ca5(PO4)3F (Calcium Fluorophosphate)

Marble

Recrystallized Calcite (CaCO3)

Chert (Flint)

Silicon Dioxide (SiO2)

Vuggy Limestone

Carbonate Sedimentary Rock with Vuggy Porosity (CaCO3)

Limestone Pebble

Limestone (Calcium Carbonate - CaCO3)

Pyrite in Limestone

Iron Sulfide (FeS2) in Calcium Carbonate (CaCO3)

Weathered quartz-rich rock, possibly chert or milky quartz

Mostly microcrystalline or crystalline quartz (SiO₂), identification uncertain from photograph

Flint / Chert Nodules in Limestone

Cryptocrystalline Quartz (SiO2) within Carbonate Rock

Fossilized Brachiopod

Brachiopoda (Phylum)

Scallop Shell Fossil

Pecten sp.

Chert Concretion

Microcrystalline Quartz (SiO2) in Carbonate Matrix

Brown Chert

Microcrystalline Quartz (SiO2)

Chert / Flint

Microcrystalline or cryptocrystalline quartz (SiO2)

Quartzite

Quartzite (SiO2)

Travertine

Terrestrial Sedimentary Limestone (CaCO3)

Quartz-rich vein rock, likely milky quartz in weathered host rock

Milky quartz (SiO₂), probably with weathered feldspar and iron-oxide staining

Weathered limestone

Limestone, predominantly calcite (CaCO₃)

Fossiliferous Limestone

Calcium Carbonate (CaCO3) - Limestone

Fossiliferous Limestone

Limestone (Calcium Carbonate - CaCO3)

Veined Limestone

Calcite-veined Limestone (CaCO3)

Fossiliferous Limestone

Fossiliferous Limestone (Sedimentary Rock)

Fossiliferous Limestone

Limestone (CaCO3 - Calcium Carbonate)

Fossiliferous Limestone

Bioclastic Limestone (composition: CaCO3)

Limestone Pebble

Limestone (Calcium Carbonate, CaCO3)

Slickenside in Limestone

Tectonized Limestone / Calcite (CaCO3)

Fossiliferous Limestone

Fossiliferous Limestone (containing bioclasts)