Rounded beach pebble
Lithology indeterminate; likely fine-grained sandstone, mudstone, or weathered volcanic rock
sedimentary
Category
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Crushed Granite and Quartz Gravel
Composite Igneous and Silicate Rock Aggregate
igneous
Pet Rock (Man-made Quartzite or Granite Cobble)
Silicon dioxide (SiO2) mixture; commonly composed of Quartz, Feldspar, and Mica
igneous or metamorphic (base stone); anthropogenic (decoration)
Beach Pebble Quartzite / Chalcedony Pebble
Silicon Dioxide (SiO2)
metamorphic
Sandstone (River Cobble)
Sandstone (primarily composed of silica, SiO2)
sedimentary
Sandstone (with Iron Staining)
Clastic sedimentary rock (primarily Quartz - SiO2)
sedimentary
River Pebbles / Mudstone
Sedimentary Rock / Silty Claystone
sedimentary
Sandstone (with Calcite or Silica veins)
Clastic sedimentary rock (primarily SiO2)
sedimentary
Sandstone
Sandstone (SiO2-rich framework with variable matrix)
sedimentary
Sandstone
Arenite (SiO2 based)
sedimentary
Beach Pebble (Nephrite Jade / Chalcedony)
Ca2(Mg,Fe)5Si8O22(OH)2 / SiO2
metamorphic
Quartz Pebble (Citrine or Iron-stained Quartz)
Silicon Dioxide (SiO2)
mineral
River Pebble (Granite / Sandstone Cobble)
Stream-rounded Rock Pebble
sedimentary
Diorite (Salt and Pepper Rock)
Diorite
igneous
Herkimer Diamond
Quartz (Silicon Dioxide, SiO2)
mineral
Clear Quartz (Rock Crystal)
Silicon Dioxide (SiO2)
mineral
Banded Slate
Slate (Metamorphosed Siltstone/Mudstone)
metamorphic
Granite
Phaneritic plutonic rock (composed of quartz, feldspar, and mica)
igneous
Sandstone
Arenite (SiO2 principal)
sedimentary
Shale (or Mudstone)
Clay mineral aggregate / Fine-grained siliciclastic sedimentary rock
sedimentary
Sandstone
Arenite (SiO2 primarily)
sedimentary
Red Sandstone
Arenite (Ferruginous Sandstone)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Siltstone or Limestone Beach Pebble
Siltstone / Micritic Limestone
sedimentary
Sandstone
Clastic sedimentary rock (primarily SiO2)
sedimentary
Sandstone
Arenite (variable SiO2 composition)
sedimentary
Sandstone (Ferruginous)
Sandstone (Clastic sedimentary rock, predominantly SiO2 with Fe2O3 cement)
sedimentary
Sandstone (Quartzose Sandstone)
Clastic sedimentary rock (primarily SiO2)
sedimentary
Sandstone (specifically Arkose or Ferruginous Sandstone)
Sandstone (SiO2 predominant)
sedimentary
Painted River Rock
Polished fluvial clast with acrylic/synthetic pigment coating
Sedimentary or Metamorphic (base substrate)
River Pebble (Greywacke / Basalt Pebble)
Indeterminate Rounded Pebble (composed of quartz, feldspar, or mafic minerals)
sedimentary
Quartz Crystal (specifically a Double-Terminated variety)
Silicon Dioxide (SiO2) - Low Quartz
mineral
Granite
Phaneritic Plutonic Felsic Rock
igneous
River Cobble (likely Metasedimentary)
Metasedimentary Rock / Quartz-rich Sandstone
metamorphic
Sandstone
Arenite (SiO2 based)
sedimentary
Sandstone
Clastic sedimentary rock (Quartz arenite/Arkose)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone (with Iron Staining)
Clastic sedimentary rock (primarily Quartz with Hematite/Limonite oxides)
sedimentary
Tumbled dark stone, likely basalt
Basalt; chiefly plagioclase feldspar, pyroxene, and minor olivine or iron oxides
igneous
Sandstone
Arenite (primarily SiO2)
sedimentary
Basalt
Basalt
igneous
Black obsidian (probable)
Volcanic glass; primarily SiO₂-rich rhyolitic composition
igneous