Limestone

Pebble (likely Limestone or Siltstone)

Lithic fragment (calcareous or siliciclastic)

Chert or silicified limestone nodule

Microcrystalline quartz (SiO₂), possibly calcareous chert

Quartz (chalcedony variety) or Limestone with Quartz Veins

SiO2 (for Quartz/Chalcedony); CaCO3 (for Limestone)

Tan chert or silicified limestone fragment

Microcrystalline quartz (SiO₂), possibly calcareous chert

Tumbled fossil-bearing limestone or chert

Microcrystalline calcite (limestone), possibly silicified; fossil fragments visible

Polished banded limestone or marble

Calcite-rich carbonate rock; chiefly CaCO₃

Likely calcite fragment

Calcite (CaCO₃), possibly limestone or marble

Small rounded pebble, likely limestone or chalk

Calcium carbonate, predominantly calcite (CaCO₃)

Calcite-rich limestone (likely crystalline limestone/marble)

Calcite, CaCO₃; likely recrystallized carbonate rock

Fossiliferous limestone

Bioclastic limestone, chiefly calcite (CaCO₃), with a visible fossil shell or fossil fragment

Weathered chert or flint nodule

Microcrystalline quartz (SiO₂), commonly with chalcedony and minor iron oxides

Porous limestone (likely fossiliferous or reef limestone)

Calcite-rich carbonate rock; predominantly CaCO₃

Weathered limestone fragment

Limestone, predominantly calcite (CaCO₃)

Gray Limestone Pebble

Calcium Carbonate (CaCO3)

Chert (Nodule)

Silicon Dioxide (SiO2)

Fossiliferous Limestone

Calcium Carbonate (CaCO3) with Organic Inclusions

Fluorite

Calcium fluoride (CaF2)

Lapis Lazuli

Lazurite-rich metamorphic rock ((Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)

Lapis Lazuli

Lapis Lazuli (Complex aggregate including Lazurite: (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)

Coral Fossil Rock (Syringopora)

Syringopora (Organ-pipe Coral fossil in Limestone matrix)

Likely weathered limestone fragment

Limestone, composed mainly of calcite (CaCO₃)

Weathered limestone fragment

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

Tumbled limestone pebble

Micritic limestone, chiefly calcium carbonate (CaCO₃; calcite)

Limestone (with crushed gravel)

Limestone (Calcium Carbonate, CaCO3)

Limestone (or Calcite Pebble)

Calcium Carbonate (CaCO3)

Limestone (Fossiliferous)

Calcium Carbonate (CaCO3) - Bioclastic Limestone

Limestone (Micrite/Chalky variety)

Calcium Carbonate (CaCO3)

Quartz Geode

Silicon Dioxide (SiO2)

Fossil Coral (Silicified)

Anthozoa (Silicified Scleractinia or Tabulata)

Crinoid Fossil Fragment

Crinoid stem fossil (Echinodermata)

Herkimer Diamond

Double-terminated Quartz (Silicon Dioxide, SiO2)

Chert (Nodule)

Microcrystalline Quartz (SiO2)

Optical Calcite

Calcium Carbonate (CaCO3)

Chert (likely Flint)

Cryptocrystalline Quartz (SiO2)

Chert Nodule / Flint

Microcrystalline Quartz (SiO2)

Chert (Flint variety)

Microcrystalline Silica (SiO2)

Chert (Nodule)

Silicon Dioxide (SiO2)

Weathered limestone or calcareous sandstone

Calcite-rich carbonate rock, chiefly calcium carbonate (CaCO₃), possibly with quartz grains

Weathered limestone or dolostone

Calcite-rich limestone (CaCO₃), possibly dolomite-bearing

Likely limestone or pale sandstone fragment

Calcite-rich carbonate rock (limestone) or quartz-rich sandstone; image is insufficient for confident species identification

Likely limestone or marble fragment

Calcite-rich carbonate rock; possibly marble (CaCO₃)

White limestone, possibly chalky limestone

Calcite-rich carbonate rock; predominantly calcium carbonate (CaCO₃)