Pale blue-gray quartz-rich pebble (tentative)
Quartz, SiO₂, possibly chalcedony or a weathered metamorphic fragment
mineral
Category
Synthetic (Not A Natural Rock)
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Shale (possibly Carbonaceous or Oil Shale)
Laminated Mudstone (primarily clay minerals and quartz)
sedimentary
Yellow Quartz (Chalcedony)
Quartz / Chalcedony (Silicon Dioxide, SiO2)
mineral
Boulder Opal
Precious Opal in Ironstone (Amorphous Hydrated Silica, SiO2·nH2O)
Mineral
Quartz
Silicon Dioxide (SiO2)
mineral
Sandstone
Clastic Sedimentary Rock
sedimentary
Sandstone
Arenite
sedimentary
Mixed river-worn rock and mineral collection
Mostly quartz/quartzite, feldspar-bearing granitoid, chert, and mafic volcanic rocks; exact species vary by pebble
igneous, sedimentary, metamorphic, mineral
Chert / Chalcedony Pebble
Cryptocrystalline Quartz (SiO2)
sedimentary
Chalcedony Pebble
Silicon Dioxide (SiO2)
mineral
Quartz Pebble (Citrine or Iron-stained Quartz)
Silicon Dioxide (SiO2)
mineral
Green Aventurine
Silicon Dioxide (Quartz) with Fuchsite inclusions (SiO2 + K(Al,Cr)2(AlSi3O10)(OH)2)
metamorphic
Tumbled dark stone, likely basalt
Basalt; chiefly plagioclase feldspar, pyroxene, and minor olivine or iron oxides
igneous
Chert / Flint Pebble with Fossil Cavity
Silicon Dioxide (SiO2)
sedimentary
Quartz Pebble
Silicon Dioxide (SiO2)
mineral
Pink Granite River Rock
Phaneritic Felsic Igneous Rock (Granite)
igneous
Granite (River-worn pebble)
Phaneritic plutonic rock (SiO2 + Al2O3)
igneous
Sandstone (likely Fossiliferous)
Arenite / Fossiliferous Sandstone (SiO2 composition)
sedimentary
Sandstone
Sedimentary Rock (Quartz arenite)
sedimentary
Red Granite
Phaneritic Felsic Igneous Rock
igneous
Granite
Phaneritic Felsic Igneous Rock
igneous
Pink Granite
Granite (Phaneritic intrusive rock)
igneous
Granite
Phaneritic Igneous Rock (Granite)
igneous
Pink Granite
Granite (Phaneritic igneous rock)
igneous
Shale
Fissile mudrock (composed of clay-sized particles and detrital grains)
sedimentary
River Pebble (Granite / Sandstone Cobble)
Stream-rounded Rock Pebble
sedimentary
Pumice
Pumice (a vesicular volcanic glass)
igneous
Red Granite
Phaneritic Felsic Igneous Rock
igneous
Smoky Quartz
Silicon Dioxide (SiO2)
mineral
River Rock (Sandstone or Quartzite)
Clastic Sedimentary Rock / Quartzite
sedimentary
Sandstone
Sandstone (principally SiO2)
sedimentary
Sandstone (Ferruginous)
Arenite (composed primarily of SiO2 with Fe2O3 staining)
sedimentary
Amethyst (Agate/Chalcedony variety)
Silicon Dioxide (SiO2) with iron impurities
mineral
Amethyst
Silicon Dioxide (SiO2)
gemstone
Shale
Argillaceous Sedimentary Rock
sedimentary
Shale (sub-type: Carbonaceous Shale)
Lutaceous Sedimentary Rock
sedimentary
Epidotite (Unakite-related)
Epidote-rich rock
metamorphic
Yellow Quartz (Citrine or Iron-stained Quartz)
Silicon Dioxide (SiO2)
mineral
Quartzite
Metamorphic Rock (composed primarily of Quartz, SiO2)
metamorphic
Beach Pebble (Basalt/Greywacke)
Amygdaloidal Basalt
igneous
Sandstone Beach Pebble
Clastic Sedimentary Rock (primarily Quartz with Iron Oxide coating)
sedimentary
Jasper in Quartz (River Cobble)
Silicon Dioxide (SiO2) with Ferric Iron inclusions
sedimentary