Quartz (Gravel)
Silicon Dioxide (SiO2)
mineral
Category
Not A Geological Specimen
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Banded Iron Formation (Jaspilite)
Banded Iron Formation (BIF); predominantly Hematite (Fe2O3) and Magnetite (Fe3O4) with Chert/Jasper (SiO2)
sedimentary
Amber
Succinite (C10H16O)
mineral
Quartzite
Quartzite (composed primarily of SiO2)
metamorphic
Dalmatian Stone
Dalmatian Jasper / Feldspathic Igneous Rock
igneous
Bauxite
Alumina-rich rock (consisting of Gibbsite, Boehmite, and Diaspore)
sedimentary
Chert (Jasper variation)
Microcrystalline Quartz (SiO2)
sedimentary
Chert (specifically Jasper/Carnelian Agate)
Microcrystalline Quartz (SiO2)
sedimentary
Snowflake Obsidian
Obsidian with Cristobalite inclusions (70–75% SiO2)
igneous
Banded Iron Formation (BIF) / Iron Ore
Banded Iron Formation (composed primarily of Hematite (Fe2O3) and Magnetite (Fe3O4) with Quartz/Chert)
sedimentary
Diamond (Cut Specimen)
Diamond (pure carbon, C)
mineral
Liesegang Ring Siltstone
Siltstone with iron oxide Liesegang bands
sedimentary
Lapis Lazuli
Na8(Al6Si6O24)S2 (Lazurite is the primary constituent mineral)
metamorphic
Chalk
Micrite (primarily Calcium Carbonate, CaCO3)
sedimentary
Geode (Calcite or Quartz)
Silicon Dioxide (SiO2) or Calcium Carbonate (CaCO3)
sedimentary
Porphyritic Andesite
Andesite (Porphyry)
igneous
Titanium Quartz (Rough)
Titanium-included Silicon Dioxide (SiO2 + Ti)
mineral
Pumice
Pumice (Felsic volcanic rock)
igneous
Iron Ore / Ironstone Concretion
Mixture of iron oxide/hydroxide minerals, likely some combination of Hematite (Fe2O3), Goethite (α-FeOOH), and Limonite (a general term for hydrated iron oxides of variable composition) or potentially Bauxite (a mixture of aluminum hydroxides, often with iron oxides, (Al(OH)3) and FeO(OH)). The visual characteristics strongly suggest iron-rich material.
Mineral, specifically an iron ore
Quartz (likely milky quartz or a stained variety)
Silicon Dioxide (SiO₂)
Mineral
Sandstone (Quartzite-rich River Cobble)
Clastic sedimentary rock (primarily SiO2)
sedimentary
Green Aventurine
Silicon Dioxide (SiO2) with Fuchsite inclusions
metamorphic
Blue Agate (Dyed)
Silicon Dioxide (SiO2) - Cryptocrystalline Quartz
mineral
Grape Agate
Botryoidal Amethystine Chalcedony (SiO2)
mineral
Trace Fossil (Lichenandites or Rhynie Chert Chert with Microfossils)
Trace fossil in microcrystalline quartz (SiO2)
fossil
Gold
Native Gold (Au)
mineral
Granite Water-worn Cobble
Felsic intrusive igneous rock (Phaneritic)
igneous
Granite Water-Worn Pebble
Phaneritic Felsic Igneous Rock
igneous
Fossiliferous Limestone
Biogenic Calcium Carbonate (CaCO3)
sedimentary
Sandstone
Arenite (SiO2 principal composition)
sedimentary
Feldspar-rich Granite (Pink Granite)
Phaneritic Felsic Igneous Rock
igneous
Ferruginous Sandstone
Clastic Sedimentary Rock (Iron-rich)
sedimentary
Granite Pebble
Felsic Plutonic Rock (primarily Quartz, Feldspar, and Mica)
igneous
Granite Pebble
Granite (Phaneritic Quartz-Feldspar intrusive rock)
igneous
Chert Nodule
Microcrystalline Quartz (SiO2)
sedimentary
River Pebble (Gneiss or Granite)
Metamorphic Rock (likely Gneiss or Granitic composition)
metamorphic
Granite Pebble
Granite (Felsic Plutonic Rock)
igneous
Fossilized Brachiopod/Bivalve in Limestone
Brachiopoda or Bivalvia fossil in Calcite/Limestone (CaCO3)
sedimentary
Granite Cobble
Phaneritic Felsic Igneous Rock
igneous
Tourmalinated Quartz
Silicon Dioxide (SiO2) with Schorl inclusions (NaFe2+3Al6(BO3)3Si6O18(OH)4)
mineral
Clear Quartz (Rock Crystal)
Silicon Dioxide (SiO2)
mineral
Limestone with Fossil Impression
Calcium Carbonate (CaCO3)
sedimentary