Limestone

Tumbled limestone or marble fragment

Calcite (CaCO₃), likely marble; possibly compact limestone

Fossiliferous limestone with a fossil sea urchin

Bioclastic limestone containing an echinoid fossil (class Echinoidea)

Fossil brachiopod in limestone

Brachiopoda; commonly a spiriferid or strophomenid brachiopod preserved in calcite-rich limestone

Limestone Pebble

Sedimentary Calcium Carbonate (CaCO3)

Fossiliferous limestone

Calcite-rich limestone (primarily CaCO₃), possibly containing fossil fragments

Iron-stained limestone or coral fragment

Calcite-rich carbonate rock; chiefly CaCO₃ (exact identification is uncertain from the image)

Weathered limestone fragments

Limestone, primarily calcite (CaCO₃)

Lapis Lazuli

Lapis Lazuli (a rock type, not a single mineral, composed primarily of lazurite, calcite, and pyrite)

Tumbled fossiliferous limestone

Crinoidal limestone, chiefly calcite (CaCO₃), with fossil echinoderm fragments

Fossiliferous Limestone with Crinoid Stem

Bioclastic Limestone (CaCO3)

Weathered limestone

Calcitic limestone, mainly calcium carbonate (CaCO₃)

Tumbled white-gray stone, likely calcite or marble

Calcite (CaCO₃), possibly fine-grained marble (recrystallized calcite)

Coral fossil (likely fossilized reef coral)

Calcitic coral; commonly fossilized Scleractinia or related colonial coral

Fossilized bivalve shell

Fossil mollusk, likely an oyster or similar cemented bivalve; original shell mostly calcite (CaCO₃)

Tumbled chert or jasper nodule

Microcrystalline quartz (SiO₂), likely iron-stained chert/jasper

Chert or flint with chalcedony/quartz veins

Microcrystalline silica: primarily quartz (SiO₂), including chalcedony; possible fossiliferous limestone or silicified material

Chert (Flint) Nodule

Cryptocrystalline Quartz (SiO2)

Chert (Tan/Grey)

Chert (Silicon Dioxide, SiO2)

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Fossiliferous Limestone Pebble

Limestone with fossil inclusion

Limestone (specifically Carboniferous Limestone)

Calcium Carbonate (CaCO3)

Limestone (specifically Dolomitic Limestone)

Calcium Magnesium Carbonate (CaMg(CO3)2)

Fossiliferous Limestone (Crinoidal Limestone)

Biogenic Limestone (Calcium Carbonate, CaCO3)

Fossiliferous Limestone (Crinoidal Limestone)

Bioclastic grainstone (CaCO3)

Chert (Nodule)

Silicon dioxide (SiO2) - Cryptocrystalline Quartz

Fossilized Blastoid

Pentremites (Class Blastoidea)

Weathered fossiliferous limestone

Limestone, primarily calcite (CaCO₃), possibly containing fossil fragments or stylolites

Polished fossiliferous limestone

Bioclastic limestone, commonly fossil-rich micrite or wackestone

Chalky limestone

Micritic limestone, predominantly calcite (CaCO₃)

Fossiliferous Limestone

Calcium Carbonate (CaCO3) with Biogenic Fragments

Fossiliferous Limestone

Calcite-rich Fossiliferous Limestone (CaCO3)

Limestone with Fossil Inclusions

Sedimentary Carbonate Rock (CaCO3)

Limestone with Calcite Crystals

Calcium Carbonate (CaCO3)

Carved limestone architectural fragment

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

Polished fossiliferous stone egg, likely fossiliferous limestone or marble

Unidentified carbonate rock; likely calcite-rich limestone (CaCO₃), possibly fossil-bearing

Chert / Flint

Microcrystalline Quartz (SiO2)

Chert (Nodule)

Chert (primarily Microcrystalline Quartz - SiO2)

Fossil coral fragment (probable)

Recrystallized fossil coral, commonly scleractinian or tabulate coral; exact identification requires magnification and locality

Rounded chert or silicified limestone pebble

Microcrystalline quartz (chalcedony/chert), possibly replacing limestone; SiO₂

Fossiliferous Limestone (Chertified Limestone)

Calcium Carbonate (CaCO3) often replaced by Microcrystalline Silica (SiO2)

Oolitic Limestone

Oosparite / Oolitic Calcarenite (CaCO3)

Weathered iron-rich limestone or calcareous sandstone

Calcite-rich carbonate rock, possibly ferruginous limestone (CaCO₃ with iron oxides)