Organic Gemstone (Not A Rock)

Pyrite (Fool's Gold)

Iron Disulfide (FeS2)

Orange Calcite

Calcium Carbonate (CaCO3)

Pyrite

Iron Sulfide (FeS2)

Limonite (Iron Ore)

FeO(OH)·nH2O (Hydrous ferric oxide)

Herkimer Diamond (Quartz Crystal)

Silicon Dioxide (SiO2)

Amethyst

Silicon Dioxide (SiO2) with traces of Iron and Manganese

Obsidian

Volcanic Glass (SiO2)

Amethyst (Rough)

Silicon Dioxide with iron impurities (SiO2)

Sodalite-rich Syenite (Sunset Sodalite)

Sodalite-Syenite (Na8[Al6Si6O24]Cl2 with KAlSi3O8)

Quartzite Pebble

Quartzite (mostly SiO2)

Quartzite with Feldspar

Quartzite (mainly SiO2) with inclusions of Potassium Feldspar (KAlSi3O8)

Desert Rose (Baryte or Selenite variant)

Barium Sulfate (BaSO4) or Gypsum (CaSO4·2H2O) with Sand inclusions

Ferruginous Sandstone (Red Sandstone)

Arenite with Hematite/Limonite cement

Sandstone (Quartzite-rich Pebble)

Arenite (composed primarily of SiO2)

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Pyrite

Iron Sulfide (FeS2)

Basalt (River Stone/Pebble)

Basalt (Extrusive Igneous Rock)

Unakite

Unakite (Altered Granite consisting of Orthoclase KAlSi3O8, Epidote Ca2(Al,Fe)3(SiO4)3(OH), and Quartz SiO2)

Basalt Pebble

Basalt

Carnelian

Carnelian (Silica, SiO2)

Amethyst (Tumbled/Weathered Quartz)

Amethyst (SiO2 with iron impurities)

Chert (specifically Flint or Jasper variant)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Banded Chert (Jasper)

Silicon Dioxide (SiO2)

Sandy Ironstone

Ferruginous Sandstone

Beryl (Variety Mix)

Be3Al2(Si6O18)

Magnetite (Iron Ore)

Magnetite (Fe3O4)

Granodiorite (or Granite) Pebble

Phaneritic Felsic Igneous Pebble

Dendritic Agate

Silicon Dioxide (SiO2) with inclusions of manganese or iron oxides

Greenstone (Epidosite or Altered Basalt)

Epidosite (Ca2(Al, Fe)3(SiO4)3(OH))

Basalt Pebble

Extrusive Mafic Igneous Rock

Limonite (Iron Ore)

Limonite (FeO(OH)·nH2O)

Peach Moonstone

Potassium Aluminum Silicate, KAlSi3O8

Basalt

Basalt (Mafic volcanic rock)

Bauxite

Bauxite (Al(OH)3, γ-AlO(OH), and α-AlO(OH))

Bauxite

Bauxite (Al2O3·nH2O)

Herkimer Diamond

Quartz (Silicon Dioxide, SiO2)

African Turquoise

African Turquoise (a trade name for Jasper, a variety of Chalcedony: SiO2)

Smoky Quartz Cluster

Silicon Dioxide (SiO2)

Jasper

Jasper (Silicon Dioxide, SiO2)

Yellow Sapphire or Citrine

Al2O3 (Corundum) or SiO2 (Quartz)

Limonite (Iron Ore)

Hydrated Iron(III) Oxide-Hydroxide (FeO(OH)·nH2O)

Quartzite

Quartzite (SiO2)