Organic Gemstone (Not A Rock Or Mineral)

Limestone

Calcium Carbonate (CaCO3)

Carnelian

Carnelian (a variety of Chalcedony, SiO2)

Prehnite

Ca2Al(AlSi3O10)(OH)2 (Calcium Aluminum Silicate hydroxide)

Red Chert (Jasper)

Silicon Dioxide (SiO2) with iron oxide inclusions

Chert (Jasper/Chalcedony)

Microcrystalline Quartz (SiO2)

White Quartz

Silicon Dioxide (SiO2)

Chert (Nodule)

Silicon Dioxide (SiO2)

Turquoise in Matrix

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

Lignite (Brown Coal)

Humic Lignite (Carbonaceous sedimentary rock)

Black Marble

Recrystallized Limestone (CaCO3)

Chert (Jasper type)

Microcrystalline Quartz (SiO2)

Milky Quartz Pebble

Crystalline Silicon Dioxide (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Chert (Flint)

Microcrystalline Opaline Silica (SiO2)

Quartz (Vein Quartz)

Silicon Dioxide (SiO2)

Fossiliferous Limestone

Biogenic Limestone (Calcium Carbonate, CaCO3)

Carnelian Agate

Silicon Dioxide (SiO2) with iron oxide impurities

Pyrite (on host rock)

Iron Sulfide (FeS2)

Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

White Topaz

Topaz [Al2SiO4(F,OH)2]

Sodalite

Sodalite [Na8(Al6Si6O24)Cl2]

Quartz (Smoky/Milky Variety)

Silicon Dioxide (SiO2)

Amethyst (Druze)

Silicon Dioxide (SiO2) with iron impurities

Black Veined Jasper (Spiderweb Jasper)

Silicon Dioxide (SiO2)

Jasper

Jasper (Silicate - SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Chert (River Pebble)

Microcrystalline Quartz (SiO2)

Amethyst

SiO2 (Silicon Dioxide with Iron impurities)

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Ruby in Zoisite (Anyolite)

Corundum var. Ruby in Zoisite (Al2O3 + (Ca2Al3(SiO4)3(OH)))

Chert (and Flint variant)

Microcrystalline Quartz (SiO2)

Clear Quartz Crystal

Silicon Dioxide (SiO2)

Montana Moss Agate

Chalcedony (Silicon Dioxide, SiO2)

Clear Quartz (Rock Crystal)

Quartz (Silicon Dioxide, SiO2)

Orange Quartzite / Carnelian Agate

Silicon Dioxide (SiO2)

Chert (often called Flint)

Microcrystalline Quartz (SiO2)

Pyrite in Shale

Iron Sulfide (FeS2) in Argillaceous Shale

Shale or Argillite

Shale (fine-grained clastic sedimentary rock) or Argillite (low-grade metamorphic rock derived from shale)

Carnelian Agate Nodule

Silicon Dioxide (SiO2) - Carnelian Chalcedony

Chert (Jasper/Flint variety)

Silicon Dioxide (SiO2)

Aventurine

Quartzite with inclusions (SiO2 containing Fuchsite chrome mica)

Blue Kyanite

Kyanite (Al2SiO5)