Geode (Unopened Keokuk Geode)
Silicon Dioxide (SiO2) - Chalcedony / Quartz exterior
mineral
Category
Anthropogenic Sedimentary Style Organic Solid
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Precious Opal
Hydrated Silica (SiO2·nH2O)
mineral
Gastropod Fossil (Snail Internal Mold)
Gastropoda; internal mold (steinkern), often composed of Calcium Carbonate (CaCO3) or Silica (SiO2)
sedimentary
Fossiliferous Shale
Carbonaceous Shale (with potential plant/aquatic fossils)
sedimentary
Geode (Quartz)
Silicon Dioxide (SiO2)
mineral
White Opal
Hydrated Amorphous Silica (SiO2·nH2O)
Mineraloid
Petrified Wood (Jet or Coalified Wood appearance)
Silicified wood (principally SiO2) or Carbonized Wood
sedimentary
Geode Nodules / Keokuk Geode
Quartz / Chalcedony Geode (SiO2)
sedimentary
Quartz (Engineered Stone Countertop)
Silicon Dioxide (SiO2) with polymer resins
Sedimentary-like (Industrial Composite)
Coal (most likely Bituminous or Anthracite)
Coal (organic sedimentary rock)
Sedimentary
Chert (Jasper/Chalcedony mix)
Microcrystalline Quartz (SiO2)
sedimentary
White Agate (Chalcedony)
Agate (Silicon Dioxide - SiO2)
mineral
Black Onyx
Silicon Dioxide (SiO2) - Chalcedony variety
gemstone
Black Limestone
Bituminous Limestone (Calcium Carbonate - CaCO3)
sedimentary
Iron-rich ochre (red/brown hematite pigment)
Hematite, Fe₂O₃, likely mixed with clay and quartz grains
mineral
Geode Nodules / Chalcedony Geode
Silicon Dioxide (SiO2) - Amorphous to Cryptocrystalline Quartz
sedimentary
Wishing Rock (Quartz Vein in Host Rock)
Silicon dioxide (SiO2) vein in various host rocks
Igneous/Sedimentary/Metamorphic with Mineral Vein
Botryoidal Chalcedony (Agate)
Cryptocrystalline Quartz (SiO2)
mineral
Likely bituminous coal
Coal, predominantly carbon-rich organic matter with variable maceral and mineral content
sedimentary
Fossil Coral (Petoskey-style Rugose Coral)
Hexagonaria percarinata (Order: Rugosa)
sedimentary
Dendritic Jasper
SiO2 (Microcrystalline Quartz)
mineral
Opal
Hydrated Silica (SiO2·nH2O)
mineral
Druzy Quartz Geode (Partially Open)
Silicon Dioxide (SiO2) within Sedimentary Host Rock
sedimentary
Sea Shell (Mollusk Shell)
Calcium Carbonate (Aragonite/Calcite)
fossil
Coal (likely Bituminous or Lignite)
Organic Sedimentary Rock (Carbonaceous)
sedimentary
Opal (in Jewelry Setting)
Hydrated Silicon Dioxide (SiO2·nH2O)
gemstone
Banded Gneiss
Gneiss (quartz-feldspar-biotite metamorphic rock)
metamorphic
Quartzite Pebble (River Rock)
Metamorphic Quartzite (predominantly SiO2)
metamorphic
Opal
Hydrated amorphous silica (SiO2·nH2O)
mineral
Carnelian ring
Carnelian, a red-orange variety of chalcedony (microcrystalline quartz, SiO₂)
gemstone
Mixed stream gravel and cobbles
Polylithic alluvial deposit; individual clasts are not identifiable at this resolution
sedimentary
Quartz Geode
Silicon Dioxide (SiO₂)
mineral
Pyrite
Iron Disulfide (FeS2)
mineral
Pyrite in Shale
Iron Disulfide (FeS2)
mineral
Petrified Wood
Silicified Wood (SiO2)
fossil
Quartz Geode
Silicon Dioxide (SiO2) in a Secondary Formation
sedimentary
Amber (Copal)
Fossilized Tree Resin
mineraloid
Seashell (Cone Snail Shell)
Conus sp. (Calcium Carbonate, CaCO3)
fossil
Microcrystalline Limestone Pebble
Carbonate sedimentary rock (Calcium Carbonate, CaCO3)
sedimentary
Wonderstone (Liesegang Sandstone)
Silicified Sandstone with Liesegang Rings (SiO2 + FeO(OH))
sedimentary
Chert Arrowhead
Cryptocrystalline Quartz (SiO2)
sedimentary
Petrified Wood
Fossilized wood / Silicified wood
Sedimentary / Fossil