Sedimentary (Fossilized Organic Remains)

Fossilized Sea Urchin (Echinoid)

Echinoidea (Class); commonly Clypeasteroida for sand dollar types

Pearl

Aragonite (CaCO3) with Conchiolin

Limestone

Calcium Carbonate (CaCO3)

Pyrite in Shale

Iron Disulfide (FeS2)

Chert (Flint)

Silicon Dioxide (SiO2)

Chert (Field Stone)

Microcrystalline Quartz (SiO2)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Black Limestone with Calcite Veining

Bituminous Limestone (CaCO3 with Organic Carbon inclusions)

Chert (Flint)

Silicon Dioxide (SiO2)

Dendritic Agate

Silicon Dioxide (SiO2) with Manganese/Iron oxide inclusions

Amygdaloidal Basalt with Quartz/Zeolite Infill

Amygdaloidal Basalt (extrusive volcanic rock with SiO2 or CaAl2Si3O10·3H2O infill)

Ammolite

Biogenic gemstone (Aragonite, CaCO3)

Dendritic Rhodonite

Rhodonite (Manganese Silicate), (Mn,Fe,Mg,Ca)SiO3

Montana Moss Agate

Chalcedony (Silicon Dioxide, SiO2)

Chert (Flint)

Chert (SiO2)

Shale

Mudstone (composed primarily of clay minerals like kaolinite, illite, and smectite, with quartz and calcite)

Fossil Shell in Sedimentary Matrix

Bivalvia (fossil) in Calcium Carbonate Matrix

Chert (Nodule)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (often called Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Dendritic Quartz

Silicon Dioxide (SiO2) with Manganese/Iron oxide inclusions

Pyrite

Iron Sulfide (FeS2)

Orthoceras Fossil in Limestone

Orthoceras (extinct genus of cephalopods), mineralized as Calcite (CaCO3) in Fossiliferous Limestone

Cockle Shell (Fossil or Recent)

Class Bivalvia, Family Cardiidae (e.g., Cerastoderma edule for common cockle)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Coal (most likely Bituminous or Anthracite)

Coal (organic sedimentary rock)

Chert (Yellow/Tan)

Microcrystalline Quartz (SiO2)

Chert (Flint)

Chert (Silicon Dioxide, SiO2)

Fossiliferous Limestone with Brachiopods

Calcium Carbonate (CaCO3) with fossilized Brachiopoda sp. (likely Order Spiriferida or Rhynchonellida)

Chert / Jasper

Silicon Dioxide (SiO2)

Chert (specifically Tan/Gray Chert)

Microcrystalline quartz (SiO2)

Chert (Flint variety)

Silicon Dioxide (SiO2)

Chert / Flint

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Crinoid Stem Fossil

Class Crinoidea (Phylum Echinodermata), primarily Calcium Carbonate (CaCO3)

Chert (often called Flint when dark)

Sedimentary cryptocrystalline quartz (SiO2)

Chert (Black Chert/Flint)

Chert (Silicon Dioxide, SiO2)

Chert (Flint variety)

Microcrystalline Quartz (SiO2)

Ammonite Fossil (Polished Half / Cleoniceras)

Ammonoidea (Subclass), often Cleoniceras genus; fossilized with Calcite (CaCO3) and Aragonite

Chalk

Calcium Carbonate (CaCO3)

Chert (Flint)

Silicon Dioxide (SiO2)

Coal

Bituminous or Anthracite coal (carbon-rich sedimentary rock)

Dendritic Opal

Hydrated Silica (SiO2·nH2O) with Manganese or Iron Oxide inclusions

Banded Chert / Banded Jasper (likely a variety of Chert/Chalcedony)

Chert (microcrystalline quartz)