Not A Natural Rock (Man Made Composite)

Sandstone

Arenite (SiO2 primarily)

Sandstone

Arenite (SiO2 based typically)

Yellow Quartz (Citrine-colored Quartz Pebble)

Silicon Dioxide (SiO2)

Porphyritic Basalt or Spotted Pebble

Porphyritic volcanic rock with phenocrysts

Polished Tumbled Stone (Dark Chalcedony / Jasper)

Silicon Dioxide (SiO2)

Quartz Pebble

Silicon Dioxide (SiO2)

Red Jasper

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Sandstone (Ferruginous)

Arenite (Fe-rich SiO2)

Ventifact

Eolian Ventifact (often composed of basalt, chert, or quartzite)

Sandstone (with Iron Staining)

Arenite (composed primarily of SiO2 with Fe2O3 staining)

Nephrite Jade

Nephrite

Quartz (Water-worn pebble)

Silicon Dioxide (SiO2)

Clear Quartz (Milky Quartz pebble)

Silicon Dioxide (SiO2)

Sandstone

Arenite (SiO2 secondary)

River Stone (Sandstone with Oxide Banding)

Arenite with Iron/Manganese Oxide inclusions

Granite

Felsic intrusive igneous rock (Granite)

Granite

Granite (Felsic Intrusive Igneous Rock)

Pink Granite

Phaneritic Felsic Igneous Rock (Granite)

Granite

Phaneritic plutonic rock (SiO2 > 69%)

Basalt

Basalt (Mafic Extrusive Igneous Rock)

Quartz (Pebble)

Quartz (SiO₂)

Sandstone (Red Sandstone)

Clastic Sedimentary Rock (primarily SiO2 with Iron Oxide)

Smoky Quartz (with possible Feldspar inclusions)

Silicon Dioxide (SiO2)

Basalt (River Pebble)

Extrusive Mafic Igneous Rock

Vesicular Basalt

Vesicular Basalt (Mafic Volcanic Rock)

Serpentine

Antigorite/Chrysotile group (Mg3Si2O5(OH)4)

Sandstone

Arenite (SiO2 main component)

Sandstone (Ferruginous)

Arenite (primarily SiO2 with iron oxide staining/cementing)

Granite

Intrusive Felsic Igneous Rock

Possible tektite or iron-rich slag-like natural specimen

Uncertain; possibly natural glass (tektite) or magnetite-rich rock

Quartzite

Quartzite (SiO2)

Pebble

Lithic fragment / Weathered rock fragment

Shale

Mudstone (composed primarily of clay minerals like kaolinite, illite, and smectite, with quartz and calcite)

Limestone

Calcium Carbonate (CaCO3)

Likely tumbled dark volcanic rock

Probably basalt or basaltic andesite; exact identification is uncertain from the image

Shale

Fissile mudstone (rich in clay minerals and quartz)

Amethyst Geode

Quartz (Silicon Dioxide, SiO2)

Porphyritic Basalt (likely artificially dyed or altered)

Basalt with plagioclase phenocrysts (likely treated)

Limestone

Calcium Carbonate (CaCO3)

Chert / Flint Pebble with Fossil Cavity

Silicon Dioxide (SiO2)

Smoky Quartz

Silicon Dioxide (SiO2) with aluminum impurities

Vein Quartz in Basalt or Chert

Silica-veined dark lithic rock (Quartz veins in microcrystalline matrix)