Chert Nodule
Chert (SiO2)
sedimentary
Category
Not A Geological Specimen
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Satin Spar (often marketed as Selenite)
Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O
mineral
Chert / Flint
Cryptocrystalline Quartz (Silicon Dioxide, SiO2)
sedimentary
Sandstone (Quartzose Sandstone)
Clastic Sedimentary Rock (Lithic arenite / Quartz arenite)
sedimentary
Obsidian
Volcanic Glass (Amorphous Silicon Dioxide , SiO2)
igneous
Quartzite (Quartz-rich Cobble)
Quartzite (SiO2)
metamorphic
Volcanic Tuff (Breccia)
Pyroclastic Tuffaceous Rock
igneous
Conglomerate
Conglomerate (clastic sedimentary rock)
sedimentary
Conglomerate
Conglomerate (clastic sedimentary rock)
sedimentary
Iridium sand or Osmium-Iridium nugget
Iridosmine / Osmiridium (Platinoid grouping)
mineral
Rhyolite
Rhyolite (High-silica volcanic rock)
igneous
Red Jasper
Silicate (SiO2 with Hematite impurities)
sedimentary
Clear Quartz (Rock Crystal)
Silicon Dioxide (SiO2)
mineral
Clear Quartz
Silicon Dioxide (SiO2)
mineral
Clear Quartz Crystal
Silicon Dioxide (SiO2)
mineral
Clear Quartz
Silicon Dioxide (SiO2)
mineral
Bull Quartz (Milky Quartz)
Quartz (Silicon Dioxide - SiO2)
mineral
Quartz with Mica Schist (Pegmatite Specimen)
SiO2 (Silicon Dioxide) and Phyllosilicates (Biotite/Muscovite)
Igneous/Metamorphic Hybrid
Petrified Wood (Silicified Wood)
Silicified Wood / Silicon Dioxide (SiO2)
metamorphic
Jasper (specifically Yellow/Red Jasper)
Silicon Dioxide (SiO2) with iron oxide inclusions
sedimentary
Sandstone with Iron Oxide
Arenite (SiO2 with Fe2O3 inclusions)
sedimentary
Red Coral
Corallium rubrum (Calcium Carbonate, CaCO3 with Carotenoid pigments)
Mineraloid (Organic Gemstone)
Pyrite (Fool's Gold)
Iron Disulfide (FeS2)
mineral
Clear Quartz
Silicon dioxide (SiO2)
mineral
Quartzite with Iron Mineral Banding
Silicon Dioxide (SiO2) with Ferric Oxide (Fe2O3) staining
metamorphic
Native Copper with Cuprite and Quartz
Copper (Cu), Cuprite (Cu2O), Quartz (SiO2)
mineral
Quartz Pebble
Silicon Dioxide (SiO2)
mineral
Quartzite Pebble (with Iron Staining)
Quartzite (SiO2)
metamorphic
Quartz
Quartz (SiO₂ - Silicon Dioxide)
Mineral
Pyrite in Matrix
Iron Disulfide (FeS2)
mineral
Limonite after Pyrite (Pseudomorph)
FeO(OH)·nH2O following FeS2
mineral
Basalt with Calcite Veins
Basalt (containing CaCO3 inclusions)
igneous
Clear Quartz (Rock Crystal)
Silicon Dioxide (SiO2)
mineral
Bog Iron (Limonite Concretion)
Limonite (FeO(OH)·nH2O)
sedimentary
Smoky Quartz
Silicon Dioxide (SiO2)
mineral
Yellow Jasper
Silicon Dioxide (SiO2) with iron hydroxides (Goethite)
sedimentary
Peridot
Olivine (Magnesium Iron Silicate), (Mg, Fe)2SiO4
mineral
Chert / Chalcedony (Agatized)
Silicon dioxide (SiO2)
sedimentary
Jasper with Quartz Veining
Silicon Dioxide (SiO2) with iron oxide impurities
sedimentary
Ferruginous Sandstone Concretion (Ironstone Phosphorite)
Ferruginous Sandstone (variable Fe-oxide/hydroxide composition)
sedimentary
Milky Quartz Mushroom Carving
Quartz (Silicon Dioxide, SiO2)
mineral
Druzy Quartz
Quartz (Silicon Dioxide, SiO2)
mineral