Limestone

Chert (specifically Flint)

Microcrystalline quartz (SiO2)

Limestone Pebble

Sedimentary Calcium Carbonate (CaCO3)

Fossiliferous Limestone

Biogenic Sedimentary Rock (Calcium Carbonate, CaCO3)

Tumbled limestone or marble fragment

Calcite (CaCO₃), likely marble; possibly compact limestone

Iron-stained limestone or coral fragment

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

Lapis Lazuli

Lazurite-rich metamorphic rock

Lapis Lazuli Globe

Complex mixture of Lazurite ((Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2), Calcite, and Pyrite

Fossilized bivalve shell

Fossil Mollusca; likely a cemented or infaunal bivalve, possibly oyster or clam

Chert

Microcrystalline quartz (SiO2)

Chert (Smoky variety)

Microcrystalline Quartz (SiO2)

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)

Fossil Shell

Invertebrate fossil (Mollusca)

Charoite

Charoite (K(Ca,Na)2Si4O10(OH,F)·H2O)

Fossil Rugose Coral (Horn Coral)

Order Rugosa (likely Grewingkia or Heliophyllum species); Calcium Carbonate (CaCO3)

Chert (specifically Banded Chert)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Weathered limestone fragments

Limestone, primarily calcite (CaCO₃)

Weathered limestone

Calcitic limestone, mainly calcium carbonate (CaCO₃)

Rounded chert or silicified limestone pebble

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

Crinoid Fossil in Limestone

Crinoidea fossil (stalk segments) in Calcium Carbonate (CaCO3) matrix

Lapis Lazuli

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

Oolitic Limestone

Oosparite / Oolitic Calcarenite (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 / Flint

Microcrystalline Quartz (SiO2)

Chert (Nodule)

Chert (primarily Microcrystalline Quartz - SiO2)

Weathered limestone fragment

Calcitic limestone (mostly CaCO₃; possibly micritic limestone)

Weathered limestone or calcitic fossil/reef fragment

Calcite-rich limestone (CaCO₃), possibly fossiliferous limestone

Oolitic Limestone

Oolitic Limestone (Calcium Carbonate, CaCO3)

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Fossil coral fragment (probable)

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

Chert (Nodule)

Silicon dioxide (SiO2) - Cryptocrystalline Quartz

Fossilized Blastoid

Pentremites (Class Blastoidea)

Fossiliferous Limestone

Limestone (composed primarily of calcite with included fossils CaCO3)

Galena

Lead sulfide (PbS)

Fossiliferous Limestone

Calcium Carbonate (CaCO3)

White-veined gray limestone or marble

Calcite-rich carbonate rock; likely calcitic marble (CaCO₃)