Sandstone
Arenite (primarily composed of SiO2)
sedimentary
Category
Organic (Non Rock)
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Petrified Wood
Silicified Wood (SiO2)
sedimentary
Moldavite
SiO2 (+ Al2O3, FeO, K2O) - Natural Tektite Glass
gemstone
Bivalve Fossil (Fossilized Shell)
Class Bivalvia (fossilized in Calcium Carbonate/Aragonite)
fossil
River Cobble (Quartzite / Granitic Gneiss)
Metamorphic Quartzite / Granitic Gneiss
metamorphic
Quartzite
Quartzite (SiO2)
metamorphic
River Stone (likely Mudstone or Siltstone)
Lutite (Clastic sedimentary rock composed of clay and silt-sized particles)
sedimentary
Quartzite (with inclusions)
SiO2 (Silicon Dioxide) rich Metamorphic Rock
metamorphic
Chert (Jasper/Flint variety)
Silicon Dioxide (SiO2)
sedimentary
Chert (Jasper/Agate variety)
Microcrystalline Quartz (SiO2)
sedimentary
Conglomerate
Conglomerate (Sedimentary rock containing rounded clasts)
sedimentary
Limestone
Calcium Carbonate (CaCO3)
sedimentary
Fossiliferous Limestone
Carbonate Sedimentary Rock (primarily CaCO3)
sedimentary
Granite
Granite (Felsic Intrusive)
igneous
Chert (Jasper/Chalcedony Pebble)
Silicon Dioxide (SiO2)
sedimentary
Obsidian
Obsidian (principally SiO2)
igneous
Chert / Flint
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Opalite (Man-made Glass)
Synthetic Silicon Dioxide Glass (SiO2 + metal oxides)
Synthetic Mineral Simulant / Glass
Gold Ore in Matrix
Native Gold (Au) in Quartz/Limonite host rock
mineral
Quartz (Iron-stained)
Silicon Dioxide (SiO2)
mineral
Chert (Flint)
Microcrystalline Quartz (SiO2)
sedimentary
Chert (Siliceous Mudstone variant)
Microcrystalline quartz (SiO2)
sedimentary
Slag (Industrial Glass/Glassy Rock)
Anthropogenic Vitreous Material
igneous
Pyrite in Slate
Iron Sulfide (FeS2) in Slate host matrix
metamorphic
Fossiliferous Limestone
Biogenic Limestone (CaCO3)
sedimentary
Coal (Bituminous or Anthracite)
Carbonaceous sedimentary rock (primarily Carbon, C)
sedimentary
Fossiliferous Sandstone / Mudstone
Sedimentary Rock (Clastic with Fossiliferous Inclusions)
sedimentary
Limestone with Lichen
Carbonate Sedimentary Rock (primarily CaCO3)
sedimentary
Dendritic Agate (Tree Agate)
Silicon Dioxide (SiO2) with Manganese/Iron oxide inclusions
mineral
Snowflake Obsidian
Volcanic glass with Cristobalite inclusions (70–75% SiO2)
Igneous
Chert (Jasper variation)
Silicon Dioxide (SiO2)
sedimentary
Chert Pebble
Microcrystalline quartz (SiO2)
sedimentary
Chert (Iron-stained)
Microcrystalline Quartz (SiO2)
sedimentary
Precious Red Coral
Corallium rubrum (Calcium Carbonate, CaCO3)
gemstone
Limestone (or Calcite Nodules)
Calcium Carbonate (CaCO3)
sedimentary
Petrified Wood
Silicified Wood (SiO2)
fossil
Petrified Wood
Silicified Wood (mainly Quartz/Chalcedony, SiO2)
fossil
Chert / Chalcedony
Silicon Dioxide (SiO2)
sedimentary
Limestone
Calcium carbonate (CaCO3) / Limestone
sedimentary
Limestone
Sedimentary rock composed mainly of calcium carbonate (CaCO3)
sedimentary
Agatized Chert / Chalcedony
Silicon Dioxide (SiO2)
sedimentary
Chert Nodules (Jasper)
Microcrystalline Quartz (SiO2)
sedimentary