Amethyst (Hematoid Quartz)
Silicon Dioxide (SiO2) with Ferric Iron inclusions
mineral
Category
Mineralogical Specimen
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Sandstone (likely Ferruginous)
Arenite (primarily SiO2 with Fe2O3 staining)
sedimentary
Fossilized Echinoid (Sea Urchin)
Echinoidea (Class)
sedimentary
Chert (Jasper)
Microcrystalline Quartz (SiO2)
sedimentary
Chert (and Fossilized Brachiopod shell)
Sedimentary Cryptocrystalline Quartz (SiO2)
sedimentary
Granite
Granite (Phaneritic Quartz-Feldspar rock)
igneous
Obsidian
Obsidian (Volcanic Glass)
igneous
Porphyritic Rhyolite
Porphyritic Rhyolite (compositionally similar to granite)
igneous
Alkali Feldspar Granite
Alkali Feldspar Granite (KAlSi3O8)
igneous
Coquina or Fossiliferous Limestone
Fossiliferous Calcarenite (CaCO3)
sedimentary
Conglomeratic Sandstone
Clastic Sedimentary Rock
sedimentary
Synthetic Faux Fur Fursuit
Polyacrylonitrile / Polyester (Synthetic Textile)
not a rock (synthetic material/costume)
Obsidian
Obsidian (Volcanic Glass)
igneous
Polygenetic Conglomerate (or Breccia)
Clastic Sedimentary Rock
sedimentary
Sandstone Cobble
Arenite (Secondary classification based on grain size)
sedimentary
Chert / Pink Flint
Cryptocrystalline Quartz (SiO2)
sedimentary
Sandstone
Arenite
sedimentary
Milky Quartz with Mineral Inclusions
Silicon Dioxide (SiO2)
mineral
Sandstone (with Siltstone/Greywacke variations)
Sedimentary Rock (Clastic)
sedimentary
Granitic Pegmatite
Pegmatite (composed primarily of Quartz, Feldspar, and Muscovite mica)
igneous
Gastropod Fossil (Snail Steinkern)
Class Gastropoda (internal mold)
sedimentary
Mahogany Obsidian
Volcanic Glass (Amorphous Silicon Dioxide with Hematite inclusions)
igneous
Yellow Septarian (Dragon Stone)
Septarian Concretion (Calcite, Aragonite, and Limestone)
sedimentary
Agate
Agate (Silicon Dioxide, SiO2)
mineral
Fossilized Coral (Petoskey Stone / Favosites)
Favosites (extinct genus of tabulate coral)
sedimentary
Conglomerate with Fossilized Shark Teeth
Clastic sedimentary rock (Conglomerate) containing Elasmobranchii remains
sedimentary
Jasper with Chert
Silicon Dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Sandstone (with potential trace fossils)
Clastic sedimentary rock (primarily SiO2)
sedimentary
Granite (Weathered/Oxidized)
Phaneritic Felsic Igneous Rock (composed of Quartz, Orthoclase Feldspar, and Mica)
igneous
Tiger's Eye (often misinterpreted as Gold Ore in this context)
Pseudomorph of Quartz after Crocidolite (SiO2)
metamorphic
Chert (Jasper variety)
Silicon dioxide (SiO2)
sedimentary
Agate Jasper
Cryptocrystalline Quartz (SiO2) with impurities
mineral
Chalcedony (Agate)
Silicon Dioxide (SiO2)
mineral
Granitic Pebble (Glacial Erratic)
Granite
igneous
Quartzite Pebble
Quartzite (principally SiO2)
metamorphic
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
sedimentary
Chert (vuggy/nodular)
Microcrystalline Quartz (SiO2)
sedimentary
Chert (often called Flint)
Microcrystalline to cryptocrystalline quartz (SiO2)
sedimentary
Mica Schist with Quartz
Mica-Quartz Schist (Muscovite subclass)
metamorphic
Chert Nodules
Microcrystalline Quartz (SiO2)
sedimentary
Quartz Pebble
Silicon Dioxide (SiO2)
mineral
Fossil Shark Tooth
Selachimorpha (Chondrichthyes dental fossil)
sedimentary