Limestone

Chert (Flint nodule)

Chert (SiO2)

Charoite

Charoite, K(Ca,Na)2Si4O10(OH,F)·H2O

Banded Onyx (Calcite Marble)

Calcite (CaCO3) - Trap-rock or Cave Onyx

Banded limestone or marble

Calcite-dominated carbonate rock; likely banded marble (CaCO₃)

Chert (variations include Flint or Jasper)

Chert (Silicon Dioxide, SiO2)

Chert (specifically Flint)

Microcrystalline quartz (SiO2)

Chalky limestone

Micritic limestone, primarily calcite (CaCO₃)

Likely weathered flint or chert fragment

Cryptocrystalline quartz (SiO₂), possibly siliceous chert/flint

Chert (Flint)

Microcrystalline Quartz (SiO2)

Chert (Jasper/Flint Pebble)

Microcrystalline or Cryptocrystalline Silicon Dioxide (SiO2)

Light-colored limestone

Calcite-rich limestone (CaCO₃)

Limestone (with weathering rind)

Calcium Carbonate (CaCO3)

Fossiliferous Limestone Pebble

Sedimentary Rock (CaCO3)

Chert

Cryptocrystalline quartz (SiO2)

Fossiliferous Limestone

CaCO3 (principally Calcite or Aragonite)

Rounded sedimentary pebble

Likely micritic limestone or calcareous sandstone

Weathered fossiliferous limestone, possibly coral or stromatoporoid

Calcitic limestone, predominantly CaCO₃; fossil identity cannot be confirmed from one photograph

Calcite fragment

Calcite (calcium carbonate, CaCO₃), possibly weathered limestone

Rounded chert or silicified limestone pebble

Microcrystalline quartz (SiO₂), possibly fossiliferous or iron-stained carbonate host

Gray chert or silicified limestone

Microcrystalline quartz (SiO₂), possibly with calcite (CaCO₃)

Brown chert or silicified limestone fragment

Microcrystalline quartz (SiO₂), possibly occurring as chert; exact identification requires testing

Likely limestone or marble

Calcite-rich carbonate rock; chiefly calcium carbonate, CaCO₃

Chert (within Limestone matrix)

Silicon Dioxide (SiO2) within Calcium Carbonate (CaCO3)

Tumbled fossil-bearing limestone (likely crinoid or shell fragment)

Fossil carbonate; predominantly calcite (CaCO₃)

Light-colored weathered stone, possibly limestone or quartz-rich rock

Indeterminate; likely calcitic limestone (mostly CaCO₃) or quartz sandstone (SiO₂)

Weathered limestone fragment, possibly fossiliferous

Calcite-rich limestone (CaCO₃), possibly bioclastic limestone

Weathered gray stone, likely limestone

Calcite-rich limestone (CaCO₃), possibly dolomitic limestone

Fossiliferous limestone

Calcite-rich limestone (CaCO₃), likely bioclastic limestone

Polished fossiliferous limestone

Bioclastic limestone, commonly crinoidal limestone (calcite, CaCO₃)

Limestone (Crushed Gravel)

Limestone (Calcium Carbonate, CaCO3)

Tumbled cream-colored stone, likely calcite or marble

Calcite (CaCO₃), possibly recrystallized as marble

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

Decorative polished stone tile, likely white marble or limestone

Calcite-rich marble (CaCO₃), possibly veined limestone; exact identification requires testing

Charoite

Charoite (K(Ca,Na)2Si4O10(OH,F)·H2O)

Weathered limestone

Calcite-rich carbonate rock (primarily CaCO₃)

Chert (Smoky variety)

Microcrystalline Quartz (SiO2)

Fossil Shell

Invertebrate fossil (Mollusca)

Fossilized bivalve shell

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

Fossil Rugose Coral (Horn Coral)

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

Chert (specifically Banded Chert)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Dark gray flint or chert fragment

Microcrystalline quartz (SiO₂), commonly called chert or flint