River Pebbles (Quartzite / Granite Pebbles)
SiO2 (Quartz-rich detrital gravel)
sedimentary
Category
Synthetic (Not A Natural Rock)
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River Agate (Chert/Chalcedony)
Cryptocrystalline Quartz (SiO2)
sedimentary
Pumice
Pumice (volcanic glass)
igneous
Shale
Fissile mudrock (composed primarily of clay minerals and quartz)
sedimentary
Sandstone
Arenite
sedimentary
Sandstone (Heart-shaped pebble)
Sedimentary Quartz Sandstone
sedimentary
Granite
Intrusive Igneous Rock
igneous
Granite
Intrusive Igneous Rock
igneous
Sandstone
Sedimentary Rock (Quartz arenite)
sedimentary
Sandstone
Sandstone (SiO2 dominated)
sedimentary
Anthracite Coal
Anthracite (Carbon-based organic sedimentary rock transitioned to metamorphic)
metamorphic
Shale with Iron Staining
Fissile Mudrock (Sedimentary Rock)
sedimentary
Veined Quartzite Pebble (Heart-Shaped)
Metamorphosed quartz-rich sandstone with quartz veins
sedimentary
Sandstone
Arenite (SiO2 primarily)
sedimentary
Porphyritic Andesite
Andesite (Porphyritic texture)
igneous
Shale
Shale (Lutite)
sedimentary
Shale
Argillaceous Sedimentary Rock
sedimentary
Textile (Upholstery Fabric)
Woven Polyethylene/Polyester or Cotton Blend
Synthetic or Natural Fiber
Vesicular Basalt or Scoria
Basalt (extrusive volcanic rock)
igneous
Amethyst and Agate Geode Section
Silicon Dioxide (SiO2) - Crystalline Quartz and Chalcedony
mineral
Sandstone
Sandstone (composed predominantly of SiO2)
sedimentary
Beach Pebble (Basalt / Greywacke Gravel)
Mafic Volcanic Rock (Basalt)
igneous
Obsidian
Volcanic Glass
igneous
Shale
Laminated Fissile Pelite
sedimentary
Sandstone (Quartzose)
Arenite (primarily SiO2)
sedimentary
Tumbled River Pebble (Quartzite / Agate)
Silicon Dioxide (SiO2)
sedimentary
Sandstone (likely Arkose or Quartz Sandstone)
Clastic sedimentary rock (primarily SiO2)
sedimentary
Clear Quartz (Cut/Faceted Gemstone)
Silicon Dioxide (SiO2)
gemstone
Shale
Fissile Mudstone (primarily composed of phyllosilicate minerals like kaolinite, montmorillonite, and illite)
sedimentary
Vesicular Basalt (Lava Rock)
Vesicular basalt
igneous
Shale
Shale (Fissile Mudstone)
sedimentary
Sandstone
Arenite
sedimentary
Sandstone (Ferruginous)
Arenite (composed primarily of SiO2 with Fe2O3 cement)
sedimentary
Sandstone (Ferruginous)
Arenite (primarily SiO2 with iron oxide cement)
sedimentary
Red Sandstone
Arenite (predominantly Quartz with Hematite cementation)
sedimentary
River Pebble / Chert Pebble
Microcrystalline Quartz (SiO2)
sedimentary
Concrete fragment with Aggregate
Anthropogenic Concrete with Calcarious and Siliceous Aggregate
sedimentary (anthropogenic/man-made)
Sandstone (likely Quartzose type)
Clastic sedimentary rock (primarily SiO2)
sedimentary
Ferruginous Sandstone (with possible Epidote/Chlorite coloring)
Sandstone (SiO2 dominated with Fe2O3 staining)
sedimentary
Quartz-veined Diabase or Basalt Pebble
Diabase or Basalt with Hydrothermal Quartz Veins (SiO2)
igneous
Sandstone (likely Quartzose)
Arenite (primarily SiO2)
sedimentary
Rounded granite cobble
Granite; chiefly quartz, feldspar, and mica/amphibole
igneous