Pearl
Calcium Carbonate (mostly Aragonite), CaCO3 (with conchiolin)
Category
Browse organic gemstone (not a rock or mineral) specimens identified by the Rock Identifier community.
Pearl
Calcium Carbonate (mostly Aragonite), CaCO3 (with conchiolin)
Shale (with minor calcite veining)
Clastic sedimentary rock (primarily clay minerals and quartz)
Feldspar
Potassium Feldspar (KAlSi3O8)
Garnet
Almandine/Pyrope Garnet (Silicate Mineral Group)
Clear Quartz
Silicon Dioxide (SiO2)
Carnelian (Chalcedony)
Silicon Dioxide (SiO2)
Garnet (likely Almandine or Pyrope)
Garnet (Group Name), Fe3Al2(SiO4)3 or Mg3Al2(SiO4)3
Fossilized Echinoid / Sea Urchin Internal Mold
Echinoidea internal cast (steinkern)
River Stone (likely Mudstone or Siltstone)
Lutite (Clastic sedimentary rock composed of clay and silt-sized particles)
Petrified Wood
Silicified wood (Quartz replacement, SiO2)
Green Quartz / Prasiolite
Silicon Dioxide (SiO2)
Septarian Nodule
Septarian Concretion (Calcite, Aragonite, and Limestone)
Fossiliferous Limestone (Shell Fragment)
Biogenic Limestone (Calcium Carbonate / CaCO3)
Chert (River Pebble)
Microcrystalline Quartz (SiO2)
Chert (Flint)
Chert (Microcrystalline Quartz, SiO2)
Chert (Common Opal/Agatized Rock)
Microcrystalline Quartz (SiO2) with potential Chalcedony/Opaline silica
Fossilized Shark Tooth
Chondrichthyes tooth
Shale
Mudstone (composed primarily of clay minerals like kaolinite, illite, and smectite, with quartz and calcite)
Amber
Succinite
Yellow Chert (Yellow Jasper)
Silicon dioxide (SiO2)
Petrified Wood
Silicified Wood (SiO2)
Amber
Resinite (Succinite if from the Baltic); Chemical Formula: C10H16O (approximate)
Petrified Wood (Black / Carbonized)
Silicon Dioxide (Quartz/Chalcedony replacing Organic Matter)
Pale green calcite or prehnite specimen
Calcite (CaCO₃), possibly prehnite [Ca₂Al₂Si₃O₁₀(OH)₂]
Quartz Druze (Crystalline Quartz)
Silicon Dioxide (SiO2)
Garnet
Almandine (Fe3Al2(SiO4)3)
Quartz
Silicon Dioxide (SiO2)
Amethyst
Quartz (Silicon Dioxide with iron impurities), SiO2
Moonstone (Feldspar)
Orthoclase feldspar, (K,Na)AlSi3O8
Travertine
Travertine (a terrestrial form of Limestone, CaCO3)
Tree Agate
Silicon Dioxide with inclusions (SiO2)
Quartz
Silicon Dioxide (SiO2)
Amber
Succinate (Fossilized Tree Resin)
Tourmalinated Quartz
Silicon Dioxide with Tourmaline inclusions (SiO2 + Na(Fe3Al6)(Al5Si6O18)(BO33)(OH4))
Petrified Wood
Silicified wood (primarily Silicon Dioxide, SiO2)
Banded Chert / Sandstone Pebble
Microcrystalline Quartz (SiO2) / Silicified Sandstone
Fossiliferous Limestone
Calcium Carbonate (CaCO3)
Aquamarine
Beryl (Be3Al2(SiO3)6)
Chert
Chert (Microcrystalline Quartz, SiO2)
Carnelian
Carnelian (subset of Chalcedony); SiO2 with Iron Oxide impurities
Mixed tumbled gemstone collection
Varied minerals, likely including amethyst, sodalite/lapis lazuli, quartzite or aventurine, jasper, and agate/chalcedony
Quartz Pebble
Silicon Dioxide (SiO2)