Organic Gemstone (Often Associated With Sedimentary Sequences)

Jasper

Silicon Dioxide (SiO2) with impurities

Chert (Flint)

Chert (Silicon Dioxide, SiO2)

Red Coral

Corallium rubrum

Ruby (Cabochon)

Corundum (Al2O3)

Chert (Flint)

Silicon Dioxide (SiO2)

Satin Spar (Gypsum)

Gypsum (Satin Spar variety) - CaSO4·2H2O

Brown Jasper

Silicon Dioxide (SiO2) with iron oxide inclusions

Chert (Red Jasper variant)

Microcrystalline Quartz (SiO2)

Chert (with Limestone/Dolomite host)

Microcrystalline Quartz (SiO2)

Chert (Red/Pink Jasper subtype)

Silicon Dioxide (SiO2)

Limestone with Chert or Siltstone bands

Sedimentary carbonate rock (CaCO3) often with siliceous impurities

Shale or Slate

Shale (Sedimentary) or Slate (Metamorphic)

Jasper

Silicon dioxide (SiO2)

Chert

Silicon dioxide (SiO2)

Epidotite

Epidotite (Epidote content > 50%)

Chert (Field Stone)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Peridotite

Ultramafic igneous rock (primarily olivine and pyroxene)

Red Jasper

Silicon Dioxide (SiO2) with iron oxide inclusions

Glauconitic Sandstone (Greensand)

Glauconitic Sandstone ((K, Na)(Fe3+, Al, Mg)2(Si, Al)4O10(OH)2)

Fossiliferous Shale Matrix

Clastic Sedimentary Rock with Brachiopod or Mollusk shell fragments

Chert (often called Flint when found in chalk/limestone)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Banded Chert

Microcrystalline quartz (SiO2)

Pink Opal

Hydrated silica (SiO2 "n H2O)

Bloodstone

Chalcedony quartz variety Heliotrope (SiO2)

Bloodstone

Chalcedony (Variety: Bloodstone / Heliotrope), SiO2

Magnesite or Dolomite in Chert

Magnesite (MgCO3) or Dolomite (CaMg(CO3)2) nodule

Satin Spar Selenite

Gypsum (Calcium Sulfate Dihydrate, CaSO4·2H2O)

Red Jasper

Red Jasper (SiO2) with Hematite inclusions

Greenstone / Serpentinite

Serpentinite (composed largely of Serpentine group minerals, Mg3Si2O5(OH)4)

Green Chert (Jasper)

Microcrystalline Quartz (SiO2) with chlorite/epidote inclusions

Limestone

Calcium Carbonate (CaCO3)

Chalcopyrite

CuFeS2

Peridotite

Ultramafic igneous rock

Sphalerite with Siderite and Pyrite

Zinc Sulfide (ZnS) with Iron Carbonate (FeCO3) and Iron Disulfide (FeS2)

Selenite (Satin Spar)

Gypsum (CaSO4·2H2O)

Chert

Chert (Microcrystalline Quartz, SiO2)

Banded Chert

Chert (a microcrystalline variety of quartz, SiO2 with minor impurities)

Peridotite

Ultramafic intrusive igneous rock

Argillite / Mudstone

Argillaceous sedimentary rock

Yellow Jasper (Iron-stained Chert)

Silicon Dioxide (SiO2) with iron oxide (Limonite/Goethite) inclusions

Likely weathered flint or chert fragment

Cryptocrystalline quartz (SiO₂), possibly siliceous chert/flint

Greenstone

Metabasalt