Sedimentary Rock (Specifically A Clastic Sedimentary Rock Formed Into A Cobble)

Gneiss

Gneiss (High-grade Metamorphic Rock)

Chert (often called Flint or River Stone)

Microcrystalline Quartz (SiO2)

Greenstone (Greenstone River Pebble)

Greenschist (metamorphosed mafic igneous rock)

Chert (Jasper or Flint variant)

Chert (composed of microcrystalline quartz, SiO2)

Quartz Geode (with possible Manganese or Goethite coating)

Silicon Dioxide (SiO2)

Chert (Yellow Jasper variant)

Microcrystalline Quartz (SiO2)

Chalk (Calcitic)

Calcium Carbonate (CaCO3) - Biogenic Sedimentary Rock

Limestone

Calcium Carbonate (CaCO3)

Dalmatian Stone (often misnamed Dalmatian Jasper)

Aplite (with hornblende/arfvedsonite inclusions)

Pyrite on Limestone

Iron Disulfide (FeS2) in Calcium Carbonate (CaCO3) matrix

Apache Tears (Obsidian)

Volcanic Glass (SiO2 - Silicon Dioxide with impurities)

Yellow Jasper

Silicon Dioxide (SiO2)

Chalcedony (variations like Agate or Jasper)

Chalcedony (SiO₂ - microcrystalline quartz)

Black Limestone with Calcite Veining

Bituminous Limestone (CaCO3 with Organic Carbon inclusions)

Green Kyanite

Kyanite (Al2SiO5)

Quartz Geode

Silicon Dioxide (SiO2)

Quartz Vein in Pelite (Metamorphic Rock)

Hydrothermal Quartz Veining in Metasedimentary Rock (SiO2)

Green Aventurine

Aventurine Quartz (SiO2 with Fuchsite inclusions)

Dalmatian Stone (Dalmatian Jasper)

Dalmatian Stone (A variety of Perthite / Aplite)

Serpentine

Serpentinite (Mg,Fe,Ni,Al,Zn,Mn)2-3(Si,Al,Fe)2O5(OH)4

Chert (Jasper/River Stone)

Silicon dioxide (SiO2) - Microcrystalline quartz

Crinoid Fossil in Limestone

Class Crinoidea in Carbonate Matrix (CaCO3)

Chert (White Chert/Flint)

Chert (Microcrystalline or Cryptocrystalline Quartz, SiO2)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Chert (containing Quartz)

Microcrystalline Silica (SiO2)

River Quartzite Siltstone

Quartz-rich Meta-siltstone (SiO2 dominated)

Montana Moss Agate

Chalcedony (Silicon Dioxide, SiO2)

Limestone with Calcite Veins

Sedimentary Calcium Carbonate (CaCO3)

Chert (White-Tan variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Quartz

Silicon Dioxide (SiO2)

Emerald in Matrix (Quartz/Schist)

Beryl (Be₃Al₂Si₆O₁₈) with Chromium/Vanadium impurities

Quartzite

Quartzite (composed primarily of SiO2)

Jasper (Iron-stained)

Silicon Dioxide (SiO2) with iron oxide inclusions

Limestone

Sedimentary Calcium Carbonate (CaCO3)

Chert (variant Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Limestone

Calcium Carbonate (CaCO3)

Gneiss (High-Grade Metamorphic Rock)

Gneiss (primarily composed of Quartz, Feldspar, and Mica/Amphiboles)

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

Quartzite

Metamorphosed Quartz Sandstone (SiO2)

Chert (Common Opal/Jasper variety)

Microcrystalline Quartz (SiO2) with hydration

Bauxite

Al2O3·2H2O (principally composed of gibbsite, boehmite, and diaspore)

Bituminous Coal

Organic sedimentary rock (humic coal)