Organic Gemstone

Yellow Chert (Jasper)

Microcrystalline Quartz (SiO2)

Chert (and its variety Flint)

Silicon Dioxide (SiO2) - Microcrystalline or cryptocrystalline Quartz

Chert (Gravel specimen)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (specifically Chalcedony or Flint variation)

Microcrystalline Quartz (SiO2)

Chert (Iron-stained)

Microcrystalline Quartz (SiO2)

Limestone (specifically Fossiliferous or Crinoidal Limestone)

Calcium Carbonate (CaCO3) - Calcite Rock

Petrified Wood

Silicified Wood (SiO2)

Petrified Wood (Silicified Wood)

Silicified Paleoflora (mainly Quartz, SiO2)

Petrified Wood

Silicified wood (Quartz variant, SiO2)

Limonite-stained Chert

Silicon Dioxide (SiO2) with Hydrated Iron Oxide (FeO(OH)·nH2O)

Chert / River Jasper

Microcrystalline Quartz (SiO2)

Coquina / Fossiliferous Limestone

Coquina (composed primarily of Calcium Carbonate / CaCO3)

Chert (often called Flint when dark)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Pink Chert (Brecciated Jasmine/Jasper)

Silicon Dioxide (SiO2)

Chert (variations include Flint or Jasper)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Petrified Wood

Silicified Wood (SiO2)

Fossiliferous Limestone

Biogenic Limestone (Calcium Carbonate, CaCO3)

Chert (Septarian or Nodular variety)

Microcrystalline Quartz (SiO2)

Chert (Common Opal/Jasper variety)

Microcrystalline Quartz (SiO2) with hydration

Petrified Wood

Silicified wood (Quartz, SiO2)

Chert (Chert / Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Limestone

Calcium Carbonate (CaCO3)

Crushed Limestone

Calcite-rich Sedimentary Rock (CaCO3)

Tanzanite

Blue Zoisite (Ca2Al3(SiO4)(Si2O7)O(OH))

Orange Calcite

Calcium Carbonate (CaCO3)

River Stone (likely Mudstone or Siltstone)

Lutite (Clastic sedimentary rock composed of clay and silt-sized particles)

Green Calcite

Calcium Carbonate (CaCO3)

Turquoise

Hydrated phosphate of copper and aluminium (CuAl6(PO4)4(OH)8·4H2O)

Chert (variant Flint/Jasper)

Microcrystalline Opaline Silica (SiO2)

Petrified Wood

Silicified Wood (SiO2)

Petrified Wood

Silicified wood (Quartz/Chalcedony replacement of organic matter)

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Peridot

Olivine (Mg, Fe)2SiO4

Shale with Plant Fossils / Carbonaceous Shale

Laminated Mudrock (Siliciclastic)

Moss Agate

Silicon Dioxide with inclusions (SiO2 + impurities)

Emerald (Faceted Gemstone)

Beryl (Be3Al2Si6O18 with Chromium/Vanadium impurities)

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Petrified Wood

Silicified Wood (SiO2)

Petrified Wood

Silicified Wood (primarily SiO2)

Chert (specifically Jasper/Flint pebble)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Petrified Wood

Silicified Wood (SiO2)