Opal
Hydrated Amorphous Silica (SiO2·nH2O)
Category
Browse sedimentary (with some aspects of mineral replacement) specimens identified by the Rock Identifier community.
Opal
Hydrated Amorphous Silica (SiO2·nH2O)
Blue Apatite
Apatite-(CaF), Ca5(PO4)3F
Chalcedony (Agate Pebble)
Silicon Dioxide (SiO2)
Sandstone (Ferruginous)
Arenite with Iron Oxide cement (SiO2 + Fe2O3)
Sandstone
Arenite
Sandstone (Quartzose)
Arenite (Siliciclastic sedimentary rock)
Sandstone
Arenite (Siliclastic Sedimentary Rock)
Picture Jasper
Silicon Dioxide (SiO2) with iron oxide inclusions
Yellow Jasper
Jasper (Silicon Dioxide, SiO2)
Ironstone concretion / Limonitic Sandstone
Goethite/Hematite Cemented Sandstone (Hydrated Iron Oxide)
Petrified Wood (Silicified Wood)
Silicified fossil wood (SiO2)
Yellow Jasper
Silicon Dioxide (SiO2) with goethite or limonite inclusions
Chert (Yellow Jasper/Flint)
Microcrystalline Quartz (SiO2)
Biotite Schist
Biotite Schist
Limonite (Iron Ore)
Hydrated Iron(III) Oxide-Hydroxide (FeO(OH)·nH2O)
Bauxite
AlOx(OH)3-2x (mixture of Gibbsite, Boehmite, and Diaspore)
Blue Kyanite
Kyanite (Al2SiO5)
Sandstone (Quartz-rich)
Arenite (primarily SiO2)
Sandstone (likely Quartz Sandstone)
Arenite (composed primarily of SiO2)
Sandstone (likely Quartzose Sandstone)
Arenite (primarily SiO2)
Quartz (Chert/Chunky Chalcedony)
Silicon Dioxide (SiO2)
Fluorite
Calcium Fluoride (CaF2)
Quartz Mineral
Silicon Dioxide (SiO2)
Potassium Feldspar and Quartz
KAlSi3O8 (Potassium Feldspar) and SiO2 (Quartz)
Carnelian and White Quartz Bracelet
Silicon Dioxide (SiO2) - specifically Carnelian (Chalcedony) and Rock Crystal/Snow Quartz
Clear Quartz (Rock Crystal)
Silicon Dioxide (SiO2)
Amethyst Geode
Quartz (SiO₂) with iron impurities
Quartz with Iron Stains
Quartz (SiO2) with iron oxide/hydroxide staining
Kyanite in Quartz
Kyanite (Al2SiO5) with Quartz (SiO2)
Limonite (Iron-rich Siltstone / Sandstone base)
Hydrous ferric oxide mixture (FeO(OH)·nH2O)
Bauxite
Bauxite (Al2O3·2H2O)
Banded Calcite (often sold as 'Mexican Onyx' or 'Calcite Onyx')
Calcite (Calcium Carbonate, CaCO3)
Sandstone
Arenite
Sapphire (likely blue synthetic sapphire or blue glass in a ring)
Corundum (Al₂O₃), specifically the blue variety due to trace amounts of iron and titanium impurities. If synthetic, it would still be Al₂O₃.
Limonite Pseudomorph after Pyrite
Limonite (Hydrous iron oxides e.g., FeO(OH)·nH2O) pseudomorphing Pyrite (FeS2)
Sandstone (Ferruginous)
Arenite (primarily SiO2 with Fe2O3 staining)
Sandstone or Limestone
Arenite or Calcareous Sedimentary Rock
Sandstone
Arenite (primarily SiO2)
Blue Banded Agate (Dyed)
Silicon Dioxide (SiO2) - variety of Chalcedony
Native Sulfur
Sulfur (S)
Blue Calcite (commonly sold as Caribbean Calcite)
Calcium Carbonate (CaCO3)
Specular Hematite (Specularite)
Iron Oxide (Fe2O3)