Orbicular granite (likely rapakivi-type granite)
Granite; chiefly quartz, alkali feldspar, plagioclase, and biotite/hornblende
igneous
Category
Not A Natural Rock (Man Made Composite)
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Mossy Rock
Mixed lithology rock with Bryophyta (moss)
sedimentary
Dyed Agate Slice
Silicon Dioxide (SiO2)
mineral
Quartz Pebble (Feldspathic / Chert Pebble)
Silicon Dioxide (SiO2) / Potassium Feldspar (KAlSi3O8)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone
Arenite
sedimentary
Hag Stone
Perforated sedimentary rock (typically flint, chert, or limestone)
sedimentary
Crinoid Fossil in Limestone
Crinoid columnal (Class Crinoidea) in biomicrite
fossil
Sandstone
Arenite
sedimentary
Iron Slag
Ferrous slag (primarily silicates and oxides of calcium, iron, and magnesium)
Anthropogenic (Man-made industrial byproduct)
Sandstone
Sandstone (SiO2 dominated)
sedimentary
Sandstone (Calcareous or Ferruginous)
Clastic sedimentary rock (SiO2 with CaCO3 or Fe2O3 cement)
sedimentary
Chert Pebble
Chert (Microcrystalline Quartz, SiO2)
sedimentary
Sandstone
Arenite (SiO2 principal composition)
sedimentary
Sandstone
Arenite (SiO2 principal)
sedimentary
Riverstone (Sandstone Pebble)
Arenite (SiO2 with various lithic fragments)
sedimentary
Sandstone (with Calcite or Silica veins)
Clastic sedimentary rock (primarily SiO2)
sedimentary
Chert / Flint Nodule
Cryptocrystalline quartz (SiO2)
sedimentary
Fossiliferous Limestone
Fossiliferous Limestone (CaCO3)
sedimentary
Granite
Phaneritic plutonic rock (Quartz, Feldspar, Mica)
igneous
Granite Boulder
Felsic Intrusive Igneous Rock
igneous
Granite
Phaneritic Plutonic Felsic Rock
igneous
Granite
Phaneritic Plutonic Felsic Rock
igneous
Sandstone
Arenite (primarily SiO2)
sedimentary
Pink Granite
Phaneritic intrusive igneous rock (Felsic)
igneous
Amethyst Quartz
Amethyst (Silicon Dioxide, SiO2)
mineral
Chert (Jasper/Agate variety)
Microcrystalline Quartz (SiO2)
sedimentary
Sandstone
Arenite
sedimentary
Geode / Fossilized Gastropod or Shell Cast
Silicon dioxide (Quartz) replacement / fossil mold
sedimentary
Chert (Flint)
Silicon dioxide (SiO2)
sedimentary
Hag Stone (Chert/Flint with natural perforation)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Sandstone (Quartzose Sandstone)
Clastic sedimentary rock (SiO2 dominated)
sedimentary
Iron-stained weathered stone (tentative)
Undetermined; possibly weathered iron-rich basalt or concretion
mineral
Sandstone (with minor quartz and possible clay components)
Clastic Sedimentary Rock (SiO2 dominated)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale
Sedimentary rock composed of clay minerals and quartz
sedimentary
Sandstone
Arenite (SiO2 principal)
sedimentary
Amethyst
Silicon Dioxide (SiO2) with iron impurities
mineral
Shale (possibly Carbonaceous or Oil Shale)
Argillaceous Sedimentary Rock
sedimentary
Mixed Gemstone Beaded Jewelry
Various minerals (e.g., Quartz varieties like Rose Quartz, Amethyst; Peridot; Garnet; etc.)
Mineral