Not A Natural Rock

Milky Quartz Pebble

Silicon Dioxide (SiO2)

Sandstone

Arenaceous sedimentary rock

Obsidian

Volcanic Glass (Amorphous silicon dioxide with impurities)

Chert (and Jasper) Nodules in Limestone

Silicon Dioxide (SiO2) microcrystalline quartz

White druzy quartz pendant with a blue crystal accent

Quartz (SiO₂); the blue material is not identifiable from the image

Rounded gray river pebble

Likely quartz-rich metamorphic or igneous pebble; exact identification requires testing

Faceted clear gemstone ring, likely quartz or glass imitation

Unidentified colorless faceted material; quartz (SiO₂) is possible, but the image cannot distinguish it from glass or another gem

Granite (Dioritic variant)

Phaneritic Felsic Igneous Rock (primarily Quartz, Feldspar, and Mica)

Flint / Chert

Silicon Dioxide (SiO2)

Tumbled green stone, possibly serpentine

Likely serpentine-group rock (mainly serpentine minerals; identification uncertain from the image)

Sandstone

Arenite

Sandstone (Quartzose Sandstone)

Arenite (SiO2 based)

Sandstone

Arenite

Gray granite or granitic gneiss fragment

Granite; mainly quartz, feldspar, and mica (exact identification is uncertain from the image)

Sandstone (Quartzose)

Arenite (primarily SiO2)

Gold-colored gemstone ring, likely citrine or glass imitation

Indeterminate from image; possible quartz (SiO₂) or yellow glass set in gold-colored metal

Limestone

Calcium Carbonate (CaCO3)

Sandstone

Arenite

Shale with Iron Staining

Fissile Mudrock (Sedimentary Rock)

Pumice

Pumice (Amorphous volcanic glass)

Quartz Pebble (Chalcedony / Agate)

Silicon Dioxide (SiO2)

Green Sandstone Pebble (River/Beach Pebble)

Glauconitic Sandstone

Hag Stone

Perforated Quartzite or Sedimentary Pebble

Amethyst Geode

Quartz (Silicon Dioxide, SiO2)

Opalite crescent pendant

Opalite (man-made opalescent glass; not a natural mineral)

Rounded quartz-rich pebble

Likely quartzite or quartz-rich sandstone; exact identification is uncertain from the image

Sandstone (Whetstone/Sharpening Stone)

Siliciclastic Sandstone (SiO2 dominant)

Green Aventurine

Silicon Dioxide (SiO2) with inclusions of Fuchsite (K(Al,Cr)2(AlSi3O10)(OH)2)

Heart-shaped Pebble (Limestone/Quartz)

Calcium Carbonate (CaCO3) / Silicon Dioxide (SiO2)

Sandstone pebble

Clastic sedimentary rock (primarily SiO2)

Green aventurine pebble

Quartz (SiO₂) with fuchsite mica inclusions

Rounded pebble with a brown mineral or rock inclusion

Unidentified lithic pebble; the pale matrix and brown patch cannot be identified reliably from the image

Weathered quartz-rich pebble

Likely quartz-bearing granitoid or quartz-rich metamorphic rock; exact identification is uncertain from the image

Rounded, weathered pebble (likely quartz-rich rock)

Indeterminate from the image; possibly quartzite or quartz-rich sandstone

Unidentified yellow-orange mineral fragment

Possibly iron-stained quartz, calcite, or citrine; identification is uncertain from the image

Weathered golden-brown mineral/rock fragment

Indeterminate from image; possibly iron-stained quartz, feldspar, or a sulfide-bearing rock

Dyed Agate / Quartz (Tumbled)

Silicon Dioxide (SiO2) with artificial dye

Weathered brown rock fragment

Indeterminate; possibly weathered granite, gneiss, or iron-stained quartz-rich rock

Shale (possibly Carbonaceous or Oil Shale)

Argillaceous Sedimentary Rock

Pink chalcedony / quartz fragment (probable)

Microcrystalline quartz, SiO₂ (likely iron-stained chalcedony or quartzite)

Sandstone

Sandstone (composed predominantly of Quartz, SiO2)

Pink-and-white quartz-rich pebble

Quartz (SiO₂), likely massive quartz with iron-oxide staining and possible feldspar inclusions