Agatized Fossil (Druzy Agate)
Silicon Dioxide (SiO2) replacing organic matter
sedimentary
Category
Organic Gemstone (Not A Mineral)
Browse organic gemstone (not a mineral) specimens identified by the Rock Identifier community.
Septarian Nodule
Septarian Concretion
sedimentary
Glauconitic Sandstone (Greensand)
Glauconitic Quartz Arenite (containing Glauconite, (K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2)
sedimentary
Pebble
Clast (specifically a granule or small pebble)
Sedimentary
Cubic Zirconia (CZ)
Zirconium dioxide (ZrO2)
mineral
Limestone (Concretionary or Tufa)
Calcium Carbonate (CaCO3)
sedimentary
Fossil Coral (Rugosa or Solitary Coral)
Rugosa (Order), often referred to as 'Horn Coral' (Lithostrotionella or Grewingkia)
sedimentary
Chert (Holey Stone)
Microcrystalline Quartz (SiO2)
sedimentary
Garden Quartz
Included Quartz (SiO2 with accessory minerals such as Chlorite, Hematite, or Feldspar)
mineral
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Banded Chert
Cryptocrystalline Quartz (SiO2)
sedimentary
Sandstone (likely Fossilized Wood or Concrete Simulacrum)
Arenite / Silicified Wood / Anthropogenic Concrete
sedimentary
Moss Agate
Chalcedony (SiO2) with inclusions of manganese or iron oxides
mineral
Pyrite on Limestone
Iron Disulfide (FeS2) in Calcium Carbonate (CaCO3) matrix
sedimentary (matrix) / mineral (inclusion)
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Orthoceras Fossil in Limestone
Orthoceras (extinct genus of cephalopods) in Carboniferous or Devonian Limestone
sedimentary
Chert (Jasper/Limonitic Chert)
Microcrystalline Quartz (SiO2)
sedimentary
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Ferruginous Chert
Microcrystalline Quartz (SiO2) with Iron Oxides
sedimentary
Fossilized Crinoid Stem Segment
Crinoid (Phylum Echinodermata, Class Crinoidea)
sedimentary
Moss Agate
Chalcedony (Silicon Dioxide with inclusions) - SiO2
mineral
Prehnite
Prehnite (Ca2Al2Si3O10(OH)2)
mineral
Green Moss Agate
Agate (Silicon Dioxide - SiO2 with inclusions of Manganese/Iron oxides)
mineral
Chert (specifically Flint or Jasper variant)
Microcrystalline Quartz (SiO2)
sedimentary
Septarian Nodule or Mud Crack Fossil
Septarian Nodule (Concretion)
sedimentary
Fossilized Shark Tooth
Scapanorhynchus (Sand Tiger Shark relative)
sedimentary
Petrified Wood
Silicified Wood (primarily SiO2)
sedimentary
Chert (often called Flint or Jasper)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Shale
Shale (comprised mostly of clay minerals and quartz)
sedimentary
Pyrite Geode (Sparkling Druzy)
Iron Sulfide (FeS2) in Sedimentary Nodule
mineral
Pyrite in Shale
Iron Sulfide (FeS2) in Sedimentary Matrix
mineral
Pyrite (Fool's Gold)
Iron Disulfide (FeS2)
mineral
Mother of Pearl (Nacre)
Nacre (Aragonite/Conchiolin), CaCO3 + Organic Polymers
mineral
Pearl
Calcium Carbonate (Aragonite or Calcite) and Conchiolin
Mineraloid
Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2 with iron oxide inclusions)
mineral
Chert (containing Iron Oxide)
Microcrystalline Quartz (SiO2)
sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
sedimentary
Chert (with Limestone matrix)
Silicon dioxide (SiO2)
sedimentary
Feldspar
KAlSi3O8 - NaAlSi3O8 - CaAl2Si2O8
mineral
Alexandrite
Chrysoberyl (BeAl2O4 with Chromium impurities)
mineral
Quartz (Clear Quartz/Rock Crystal)
Silicon Dioxide (SiO2)
mineral
Almandine Garnet in Matrix
Almandine, Fe3Al2(SiO4)3
metamorphic