Organic Crystal (Mineraloid)

Chert (Hag Stone / Hole Stone)

Chert (Cryptocrystalline variety of Quartz, SiO2)

Petrified Wood

Silicified wood / Xylopal

Jasper (Red-Brown)

Silicon Dioxide (SiO2) with Iron Oxide impurities

Quartz Geode

Silicon Dioxide (SiO2) within a secondary sedimentary structure

Fossiliferous Limestone / Petoskey Stone (Coral Fossil)

Hexagonaria percarinata / Calcite (CaCO3)

Ironstone Concretion (Limonite/Hematite Nodules)

Ironstone (principally Limonite FeO(OH)·nH2O or Hematite Fe2O3 mixed with silica/clay)

Petrified Wood

Silicified Wood (primarily quartz/chalcedony replacing organic wood structure)

Petrified Wood

Silicified Wood (SiO2)

Amethyst Sage Agate

Silicon Dioxide (SiO2) with trace minerals (Manganese/Iron oxides)

Glauconitic Sandstone

Glauconitic Quartz-Wacke / Sandstone (Fe(II),Fe(III),Al,Mg)2-3(Si,Al)4O10(OH)2

Banded Chert

Microcrystalline Quartz (SiO2)

Limonite-stained Chert

Microcrystalline Quartz (SiO2) with Hydrated Iron Oxides (FeO(OH)·nH2O)

Petrified Wood

Silicified Wood (SiO2)

Moss Agate

Silicon Dioxide (SiO2) with inclusions of hornblende, chlorite, or manganese/iron oxides

Jasper

Jasper (Silicon Dioxide, SiO2)

Petrified Wood

Silicified Wood / Xylopal (SiO2)

Banded Chert (Jasper)

Silicon Dioxide (SiO2)

Sandy Ironstone

Ferruginous Sandstone

Quartz Geode

Silicon Dioxide (SiO2)

Green Jasper (with Quartz veining)

Jasper (Silica-rich microcrystalline variety of Quartz), formula: SiO2

Jasper (likely Brown or Brecciated)

Jasper (Silicon Dioxide, SiO2)

Blue Quartzite (Dyed)

Metamorphosed Quartz-rich Sandstone (SiO2 with organic dye)

Septarian Nodule

Septarian Concretion (Calcite, Aragonite, and Limestone)

Petrified Wood

Silicified Wood (SiO2)

Chert (White/Light Tan)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Petrified Wood

Silicified wood (Quartz/Chalcedony - SiO2)

Petrified Wood

Silicified wood (primarily Quartz/Chalcedony, SiO2)

Mookaite Jasper

Silicified Radiolarite (SiO2)

Chert (Nodular)

Chert (SiO2 - Microcrystalline Quartz)

Petrified Wood

Silicified Wood (SiO2)

Pearl

Calcium carbonate (CaCO3) + organic conchiolin (Biogenic Mineral)

Fossiliferous Limestone (containing Brachiopods)

Biogenic Limestone (Calcium Carbonate, CaCO3)

Petrified Wood

Silicified Wood (SiO2)

Glauconitic Sandstone (or Greensand)

Glauconitic Siliciclastic Rock (Containing (K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2)

Fossilized Coral

Rugose coral / Tabulate coral (Calcium carbonate, CaCO3)

Banded Chert

Cryptocrystalline Quartz (SiO2)

Chert (Chert Nodule)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Petrified Wood (Agatized/Silicified Wood)

Silicified Wood (SiO2)

Chert (specifically Tan/Brown Chert)

Chert (SiO2)

Petrified Wood

Silicified wood (Quartz replacement of organic wood structure)

Petrified Wood

Silicified Wood (SiO2)

Pearl

Calcium Carbonate (CaCO3) - Aragonite/Calcite organic gemstone