Siltstone
Siltstone (primarily composed of SiO2, Al2O3, and phyllosilicates)
Category
Browse organic gemstone (often associated with sedimentary sequences) specimens identified by the Rock Identifier community.
Siltstone
Siltstone (primarily composed of SiO2, Al2O3, and phyllosilicates)
Pyrite (Fool's Gold) in Matrix
Iron Sulfide (FeS2)
Chert / Flint
Chert (varieties include Flint)
Chert (Jasper variety)
Silicon Dioxide (SiO2)
Green Chert
Microcrystalline Quartz (SiO2)
Chert
Microcrystalline quartz (SiO2)
Banded Chert (Jasper)
Silicon Dioxide (SiO2) with iron oxide inclusions
Jasper
Microcrystalline quartz (SiO2)
Blue Agate
Chalcedony (SiO2)
Stromatolite
Biogenic sedimentary rock (Calcium carbonate / SiO2 replaced)
Chert (Flint)
Microcrystalline Quartz (SiO2)
Jasper Breccia
Silicon Dioxide (SiO2) with impurities
Chert (Flint Nodular Variety)
Microcrystalline Quartz (SiO2)
Red Sandstone Pebble
Arenite (Fe2O3 enriched)
Glauconitic Sandstone
Glauconitic Quartz Arenite
Chert (Nodular Chert)
Silicon Dioxide (SiO2)
Yellow Jasper
Quartz (Silicon Dioxide, SiO2 with impurities)
Red Jasper
Microcrystalline Quartz (SiO2)
Chert (Yellow Jasper)
Microcrystalline Quartz (SiO2)
Carnelian
Silicon Dioxide (Chalcedony variety), SiO2
Rhodochrosite
Rhodochrosite, Manganese Carbonate (MnCO3)
Pyrite
Iron Sulfide (FeS2)
Chert (Flint)
Silicon Dioxide (SiO2)
Stromatolite
Biogenic sedimentary rock
Glauconitic Sandstone (Greensand pebble)
Glauconitic Quartz Sandstone (K(Fe,Al)2(Si,Al)4O10(OH)2)
Chert (Pebble)
Microcrystalline to Cryptocrystalline Quartz (SiO2)
Chert
Microcrystalline quartz (SiO2)
Agate
Silicon dioxide (chalcedony), SiO2
Banded Chert
Cryptocrystalline Quartz (SiO2)
Chert
Chert (Microcrystalline Silica, SiO2)
Red Jasper (Jasper)
Silicon Dioxide (SiO2) with iron oxide inclusions
Jasper
Jasper (Silicon Dioxide, SiO2)
Chert (specifically Flint or Common Chert)
Silicon Dioxide (SiO2)
Chalk (Sedimentary Limestone)
Calcite (CaCO3)
Chert (Green Jasper)
Microcrystalline Quartz (SiO2) with iron silicate inclusions
Chert (Jasper)
Microcrystalline Quartz (SiO2)
Tumbled red chalcedony or dyed agate
Microcrystalline quartz (SiO₂), likely chalcedony/agate; vivid color may be dye-enhanced
Specular Hematite (Specularite)
Iron Oxide (Fe2O3)
Carnelian
Silicon dioxide (Chalcedony variety, SiO2)
Chert
Chert (SiO2)
Fossilized Shark Tooth
Chondrichthyes (Class) fossilized tooth
Rainbow Fluorite
Fluorite (Calcium Fluoride, CaF2)