Polished pink granite cobble
Granite, chiefly potassium feldspar, plagioclase, quartz, and biotite/hornblende
igneous
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Not A Rock (Synthetic Material)
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Sandstone with Iron Staining
Arenite (SiO2 with Fe-oxide coatings)
sedimentary
Sandstone (Ferruginous Concretion)
Arenite (with iron oxide cement)
sedimentary
Sandstone (Quartzose)
Arenite (primarily SiO2)
sedimentary
Sandstone (with Iron Staining)
Clastic Sedimentary Rock (primarily SiO2 with FeO(OH) impurities)
sedimentary
Quartzite Geode (unopened)
SiO2 (Silicon Dioxide)
metamorphic
Chert (Yellow Jasper)
Microcrystalline Quartz (SiO2)
sedimentary
Moss Agate / Chalcedony
Silicon Dioxide (SiO2)
mineral
Fossiliferous Sandstone (with Quartz patch)
Sedimentary Sandstone with Silicified Shell Fragments
sedimentary
Quartzite
Metamorphic rock predominantly composed of Quartz (SiO2)
metamorphic
Sandstone (specifically Lithic or Quartz Arenite)
Arenite (composed primarily of SiO2)
sedimentary
Milky Quartz with Iron Inclusions
Silicon Dioxide (SiO2)
mineral
Pink granite
Felsic intrusive igneous rock; mainly quartz, potassium feldspar, plagioclase, and minor mica
igneous
Sandstone with Trace Fossils
Quartz Arenite with Bioturbation (Trace Fossils)
sedimentary
Chert (within Limestone)
Silicon Dioxide (SiO2) in Calcium Carbonate (CaCO3) matrix
sedimentary
Tumbled dark stone, likely basalt or basaltic rock
Fine-grained mafic volcanic rock; commonly basalt, composed chiefly of plagioclase and pyroxene with possible olivine and iron oxides
igneous
Greenschist
Greenschist facies rock
Metamorphic
Clear Quartz
Silicon Dioxide (SiO2)
mineral
Pumice
Pumice (volcanic rock)
Igneous
Crushed Limestone (Gravel)
Calcium Carbonate (CaCO3)
sedimentary
Diorite
Intermediate Phaneritic Igneous Rock
igneous
Conglomerate
Conglomerate (clastic sedimentary rock)
sedimentary
Scoria (Lava Rock)
Scoria (extrusive volcanic rock)
igneous
Indigo Gabbro
Gabbro (Mafic Intrusive Rock)
igneous
Tumbled purple agate (likely grape agate or amethystine chalcedony)
Microcrystalline quartz, SiO₂; purple coloration commonly from iron, manganese, or inclusions
mineral
Amethyst Quartz
Silicon Dioxide (SiO2)
mineral
Chert (White Chert/Flint)
Silicon Dioxide (SiO2)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Diabase
Diabase (also known as Dolerite)
igneous
Granite Pebble
Granite (Phaneritic Quartz-Feldspar Plutonic Rock)
igneous
Granite Pebble
Phaneritic plutonic rock (Quartz, Feldspar, Mica)
igneous
Slate
Foliated Metamorphic Rock (composed of quartz, illite, chlorite)
metamorphic
Coquina or Fossiliferous Conglomerate
Bioclastic Rudstone (variable composition)
sedimentary
Quartzite Pebble
Quartzite (SiO2)
metamorphic
Mica Schist
Mica Schist (Main mineral constituents: Muscovite/Biotite, Quartz, Feldspar)
metamorphic
Epidosite
Epidosite (composed mainly of Epidote - {Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH))
metamorphic
Chert (Jasper/Ironstone variety)
Silicon Dioxide (SiO2) with iron oxide inclusions
sedimentary
Fossiliferous Sedimentary Rock (Coquina/Limestone)
Fossiliferous Calcarenite / Bioclastic Limestone
sedimentary
Granite Pebble
Granite (composed primarily of Quartz, Feldspar, and Mica)
igneous
Unidentified weathered rock fragment
Likely granitic or feldspathic rock; exact identification requires clearer imaging and testing
igneous
Chert (varieties include Flint and Jasper)
Microcrystalline or cryptocrystalline Quartz (SiO2)
sedimentary
Chert (Agatized)
Silicon Dioxide (SiO2)
sedimentary