Sandstone (Whetstone/Sharpening Stone)
Siliciclastic Sandstone (SiO2 dominant)
sedimentary
Category
Not A Natural Rock (Man Made Composite)
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Sandstone (Ferruginous)
Arenite (SiO2 with Fe-oxide cement)
sedimentary
Kimberlite with Diamonds
Kimberlite (ultramafic potassic igneous rock)
igneous
Yellow Jasper (Chert) Pebble
Silicon Dioxide (SiO2) with Iron Oxides
sedimentary
Blue Dyed Agate Geode
Chalcedony (cryptocrystalline Quartz), SiO2
mineral
Sandstone
Arenite (composed primarily of SiO2)
sedimentary
Dark fine-grained rock, likely basalt
Basalt; chiefly plagioclase feldspar and pyroxene, commonly with olivine and iron oxides
igneous
Druzy Quartz
Crystalline Silicon Dioxide (SiO2)
mineral
Jasper and Agate
Microcrystalline Quartz (SiO2)
sedimentary
Polished brecciated jasper
Jasper, opaque microcrystalline quartz (SiO₂), with iron-oxide and other mineral inclusions
gemstone
Gneiss (Banded Gneiss Cobble)
Gneiss
metamorphic
Veined Sandstone with Calcite Veins
Sedimentary sandstone with hydrothermal/mineral veins
sedimentary
Granite Pebble
Granite (Plutonic Igneous Rock)
igneous
River Cobble (Quartzite or Sandstone)
Clastic sedimentary rock (primarily SiO2)
sedimentary
Sandstone
Sedimentary Clastic Rock (Quartz Arenite)
sedimentary
Sandstone (with Iron Oxide)
Quartz Arenite / Ferruginous Sandstone (SiO2 with Fe2O3)
sedimentary
Granite
Granite (composed primarily of Quartz SiO2, Potassium Feldspar KAlSi3O8, and Plagioclase Feldspar)
igneous
Pink Granite
Granite (Felsic Plutonic Rock)
igneous
Fossiliferous Mudstone / River Pebble
Sedimentary rock with trace fossil or inclusion
sedimentary
Hag Stone (Adder Stone / Geode-bearing Pebble)
Sedimentary Rock with Cavity (often Quartzite, Limestone, or Sandstone)
sedimentary
Sandstone (Ferruginous)
Sandstone (primarily SiO2 with iron oxide cement Fe2O3)
sedimentary
Aura Quartz (Coated Quartz)
Silicon Dioxide (SiO2) treated with metallic vapor
mineral
Obsidian
Volcanic Glass (Amorphous SiO2)
igneous
Dyed Agate Slice
Silicon Dioxide (SiO2) - Chalcedony variety
mineral
Amethyst Cluster
Silicon Dioxide (SiO2) with iron impurities
mineral
Smoky Quartz (Tumbled)
Silicon Dioxide (SiO2)
mineral
Smoky Quartz
Silicon Dioxide (SiO2)
mineral
Amethyst Cluster
Silicon Dioxide (SiO2 with iron impurities)
mineral
Sandstone
Sandstone (Quartzose/Feldspathic Sandstone)
sedimentary
Herkimer Diamond (Quartz)
Silicon Dioxide (SiO2)
mineral
Pumice
Pumice (Felsic vesicular volcanic glass)
igneous
Polished orbicular jasper (likely ocean jasper)
Jasper, a microcrystalline variety of quartz (SiO₂), with iron-oxide and other mineral inclusions
mineral
Sandstone
Arenite (SiO2 based with quartz, feldspar, or lithic fragments)
sedimentary
Porphyry
Porphyritic Andesite / Basaltic Porphyry
igneous
Granite
Granite (Phaneritic Quartz-Feldspar Plutonic Rock)
igneous
Granite
Granite (Phaneritic intrusive igneous rock)
igneous
Blue Agate (Dyed)
Silicon Dioxide (SiO2)
mineral
Red Sandstone
Arenite (primarily Quartz and Iron Oxide)
sedimentary
Emerald crystal in host rock
Beryl (Be3Al2Si6O18 with Chromium/Vanadium impurities)
gemstone
Likely slag or metallic industrial byproduct
Unidentified iron-rich ferrous slag; possibly magnetite-bearing slag
mineral
Granite
Granite (Felsic Plutonic Rock)
igneous
Pumice (Vesicular Lava)
Pumice
igneous