Limestone

Limestone Pebble

Calcite-rich Sedimentary Rock (CaCO3)

Massive calcite (likely limestone-derived calcite)

Calcite, calcium carbonate (CaCO₃); possibly a chalky limestone fragment

Chert

Silicon Dioxide (SiO2)

Limestone with Chert

Sedimentary Rock (CaCO3 with SiO2 inclusions)

Unidentified pale sedimentary rock, likely limestone

Calcite-rich limestone (CaCO₃), possibly fossiliferous or weathered micritic limestone

Calcite-rich limestone

Limestone, predominantly calcite (CaCO₃), possibly fossiliferous or weathered dolomitic limestone

Weathered fossiliferous limestone

Calcitic limestone, predominantly calcium carbonate (CaCO₃), possibly bioclastic limestone

Blue Spinel on Marble with Phlogopite

MgAl2O4 (Spinel) in CaCO3 (Calcite/Marble) matrix

Polished fossil coral (likely fossilized honeycomb or tabulate coral)

Fossilized tabulate coral; commonly Favosites or related genera, preserved mainly as calcite (CaCO₃)

Fossil coral, likely solitary rugose coral

Rugosa (possibly colonial tabulate coral); calcite/aragonite replaced by calcite

Chert (Flint)

Microcrystalline quartz (SiO2)

Chert

Microcrystalline or cryptocrystalline quartz

Fossiliferous Limestone

Biogenic Limestone (Calcium Carbonate, CaCO3)

Chert with Limestone

Microcrystalline Quartz (SiO2) in Calcium Carbonate (CaCO3) matrix

Limestone with Chert

Calcium Carbonate (CaCO3) with Silica (SiO2) inclusions

Fenestella Bryozoan Fossil

Fenestella (class Stenolaemata)

Chert (Nodule)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Marble

Recrystallized Calcite / Metamorphosed Limestone (CaCO3)

Limestone Pebble

Sedimentary Calcium Carbonate (CaCO3)

Fossiliferous Limestone

Limestone with embedded fossil cross-section

Likely limestone

Calcite-rich carbonate rock (CaCO₃), possibly fossiliferous or dolomitic limestone

Fossiliferous limestone

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

Weathered chert or silicified limestone nodule

Microcrystalline quartz (SiO₂), possibly replacing limestone; exact identification requires testing

Fossils in Limestone (Crinoid / Marine Invertebrate Fossil)

Fossiliferous Limestone (containing Crinoidea / Brachiopoda)

Fossilized Echinoid (Sea Urchin) or Brachiopod

Echinoidea / Invertebrate Fossil

Starfish Fossil

Asteroidea fossil

Amethyst and Limestone

Amethyst (SiO2 - Silicon Dioxide) and Limestone (CaCO3 - Calcium Carbonate)

Chert

Microcrystalline Quartz (SiO2)

Tumbled fossiliferous limestone

Bioclastic limestone, likely crinoidal or shell-rich limestone (calcite, CaCO₃)

Mixed collection of polished pebbles, including probable fossiliferous limestone

Unidentified sedimentary rocks; the gray pebble with circular fossils may be bioclastic limestone

Fossiliferous Limestone with Brachiopod

Phylum Brachiopoda in Sedimentary Matrix (CaCO3)

Brachiopod Fossil in Limestone

Phylum Brachiopoda, Class Rhynchonellata

Fossil Bivalve Shell

Class Bivalvia (e.g., Veneriidae family)

White limestone

Calcite-dominated carbonate rock (CaCO₃), possibly chalky limestone

Chert Nodule in Limestone

Microcrystalline Quartz (SiO2) within Calcium Carbonate (CaCO3)

Weathered limestone

Calcite-rich carbonate rock (mostly CaCO₃), possibly fossiliferous limestone

Gray Limestone

Carbonate rock (CaCO3)

Polished brown flint/chert (likely)

Microcrystalline quartz, SiO₂ (chalcedonic flint/chert)

Weathered limestone or chert-rich limestone

Calcitic limestone, primarily calcium carbonate (CaCO₃), possibly with microcrystalline silica and iron-oxide staining

Pyrite in Limestone

Iron Sulfide (FeS2) in Calcium Carbonate (CaCO3)

Chert (with Chalky Cortex)

Silicon Dioxide (SiO2)

Fossiliferous limestone with a shell fossil

Calcite-rich limestone (primarily CaCO₃), containing a likely fossil shell