Chert (Chalcedony/Flint)
Silicon Dioxide (SiO2)
sedimentary
Category
Organic (Non Rock)
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Limestone (River Pebble)
Calcium Carbonate (CaCO3)
sedimentary
Jasper with Hematite inclusions
Silicon Dioxide (SiO2) with Ferric Oxide (Fe2O3)
sedimentary
Conglomerate
Conglomerate (clastic sedimentary rock)
sedimentary
Puddingstone (Conglomerate)
Conglomerate (clastic sedimentary rock)
sedimentary
Snowflake Obsidian
Vitreous volcanic silicate rock (SiO2) with Spherulite inclusions
igneous
Quartzite Cobble
Quartzite (SiO2)
metamorphic
Wonderstone (Liesegang Sandstone)
Silicified Sandstone with Liesegang Rings (SiO2 + FeO(OH))
sedimentary
Quartzite
Quartzite (consisting primarily of SiO2)
metamorphic
Smurf Rock (Fictional Interpretation)
Cyanus Anthropomorphicus (Geologic Simulation)
Artificial/Fantasy Object
Grey River Stone (Quartz-rich Quartzite/Siltstone)
Quartzite / Meta-siltstone (primarily SiO2)
Metamorphic (low-grade)
Limestone with Calcite Veining
Sedimentary Carbonate Rock (CaCO3)
sedimentary
Pink Opal
Hydrated Amorphous Silica (SiO2·nH2O)
Mineral
Slag Glass (Cullet)
Amorphous Silica / Glass residue
Man-made byproduct (Non-geological)
Ethiopian Fire Opal
Hydrated Silica (SiO2·nH2O)
mineral
Quartzite
Quartzite (primarily SiO2)
metamorphic
Chert (Flint)
Chert (Cryptocrystalline Silicon Dioxide, SiO2)
sedimentary
Chert (Flint Pebbles)
Microcrystalline Quartz (SiO2)
sedimentary
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Apache Tears (Obsidian)
Volcanic Glass (SiO2 - Silicon Dioxide with impurities)
igneous
Chert (Flint)
Chert (SiO2)
sedimentary
Shale with Iron Staining
Fissile Mudrock (Sedimentary Rock)
sedimentary
Quartzite
Quartzite (SiO2)
metamorphic
Petrified Wood
Silicified Wood (primarily Chalcedony/Quartz, SiO2)
fossil
Chert (variations include Flint or Jasper)
Cryptocrystalline Quartz (SiO2)
sedimentary
Chert / Flint
Chert (Microcrystalline Quartz, SiO2)
sedimentary
Quartzite (Yellow/Tan)
Metamorphic Rock composed of Quartz (SiO₂)
metamorphic
Anthracite Coal
Low-grade metamorphic carbonaceous rock
metamorphic
Rough Emerald in Matrix
Beryl (Be3Al2Si6O18) with trace Chromium/Vanadium
mineral
Likely basaltic rock fragment
Fine-grained mafic igneous rock, probably basalt (plagioclase–pyroxene ± olivine)
igneous
Black obsidian (probable)
Volcanic glass; primarily SiO₂-rich rhyolitic composition
igneous
Chert (Jasper variety)
Microcrystalline Quartz (SiO2)
sedimentary
Ironstone Concretion (Limonite/Goethite)
Goethite/Limonite concretion (FeO(OH)·nH2O)
sedimentary
Obsidian
Obsidian (Volcanic Glass)
igneous
Obsidian
Obsidian (principally SiO2)
igneous
Pumice
Pumice (a vesicular volcanic glass)
igneous
Shale
Mudrock / Fissile Shale
sedimentary
Pyritic Mudstone
Argillaceous rock (FeS2)
sedimentary
Dark river pebble (likely basalt or andesite)
Fine-grained mafic/intermediate volcanic rock; commonly basalt (plagioclase ± pyroxene/olivine)
igneous
Fossilized Nut / Coprolite / Concretion
Trace Fossil / Permineralized Plant Material
fossil
Mahogany Obsidian
Obsidian (Volcanic Glass) with Hematite/Magnetite inclusions
igneous
Quartzite
Quartzite (SiO2)
metamorphic