Limestone

Silicified fossil-bearing limestone (likely chert/agate replacement)

Microcrystalline quartz (SiO₂) replacing carbonate rock; possible fossiliferous limestone

Fossiliferous Limestone with Crinoid Stem

Bioclastic Limestone (CaCO3)

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Druzy Quartz

Quartz (Silicon Dioxide, SiO2)

Crushed Stone Ballast

Crushed Limestone or Granite Aggregate

Chert (Flint)

Silicon dioxide (SiO2)

Lapis Lazuli (in Matrix)

Na8[Al6Si6O24]S2 (Lazurite as the primary component)

Chert (Nodule)

Microcrystalline Silica (SiO2)

Fossiliferous limestone

Calcite-rich limestone (CaCO₃), likely bioclastic limestone

Weathered gray stone, likely limestone

Calcite-rich limestone (CaCO₃), possibly dolomitic limestone

Polished fossiliferous limestone

Bioclastic limestone, commonly crinoidal limestone (calcite, CaCO₃)

Quartz-rich pebble, possibly chert or silicified limestone

Microcrystalline quartz (SiO₂), possibly chalcedony; exact identification is uncertain from the photograph

Chert (Flint)

Microcrystalline Quartz (SiO2)

Chert (or Flint)

Chert (cryptocrystalline quartz), SiO2

Calcite on Limestone

Calcium Carbonate (CaCO3) on Sedimentary Rock

Fossil Coral in Limestone

Scleractinia (Anthomastodon or similar) in Sedimentary Calcarenite

Sphalerite

Zinc Sulfide (ZnS)

Fossilized echinoid (sea urchin), likely a flint/chalk-associated test

Echinoid fossil; likely a regular echinoid such as Echinocidaris or related taxon, composed mainly of recrystallized calcite (CaCO₃)

Chert Concretion

Microcrystalline Quartz (SiO2)

Quartz-veined Limestone

Sedimentary limestone with quartz/calcite veinlets

Chert (Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Lapis Lazuli

Lapis lazuli (primary mineral: Lazurite, (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)

Chert (Flint variety)

Chert (SiO2)

Fossil Coral (Petoskey Stone or Favosites)

Favosites (specifically Hexagonaria percarinata if silica-replaced Michigan type)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Chert (with Quartz veins)

Microcrystalline Quartz (SiO2)

Rounded limestone pebble

Limestone, predominantly calcite (CaCO₃)

Fossiliferous limestone

Bioclastic limestone, primarily calcite (CaCO₃), with possible shell or coral fossil molds

Limestone with Calcite Veins

Sedimentary Calcium Carbonate (CaCO3)

Crinoid Marble

Crinoidal Limestone/Marble

Lapis Lazuli and Amazonite

Complex silicate mineral aggregates (Lazurite, Calcite, Pyrite & Microcline feldspar)

Brown Marble

Metamorphic Limestone (CaCO3)

Coquina

Biogenic Limestone (Coquina)

Fossiliferous Limestone

Bioclastic Limestone (CaCO3)

Coquina

Biogenic Limestone (Coquina)

Elephant Skin Stone

Weathered Dolomitic Limestone

Coquina

Coquina (Bioclastic Limestone)

Travertine (Tufa)

Chemical Limestone (CaCO3)

Marble

Metamorphosed Limestone (CaCO3)

Coquina

Coquina Limestone (CaCO3)

Fossiliferous Limestone with Coral Imprint

Fossiliferous Limestone (CaCO3)

Fossiliferous Limestone

Biogenic Limestone (CaCO3)