Not A Rock (Synthetic Material)

Gneiss

High-grade regional metamorphic rock

Carnelian (Polished Cabochon)

Silicon Dioxide (SiO2) with iron oxide impurities

Chert (varietal Chalcedony or Flint)

Silicon dioxide (SiO2) - Microcrystalline Quartz

Granite Pebble

Granite (composed primarily of Quartz SiO2, Feldspar KAlSi3O8, and Biotite/Hornblende)

Iron-rich weathered rock, likely limonite/goethite-bearing laterite

Limonite (variable hydrated iron oxides; chiefly goethite, α-FeO(OH))

Chert (Flint)

Silicon dioxide (SiO2)

Sandstone

Sandstone (Clastic Sedimentary Rock)

Amygdaloidal basalt (vesicular basalt)

Basalt, commonly containing amygdales of quartz, chalcedony, calcite, or zeolites

Sandstone (likely Graywacke or Siltstone variety)

Clastic Sedimentary Rock (SiO2 with assorted mineral fragments)

Sandstone (Quartz-rich)

Clastic sedimentary rock (SiO2 primary)

Rounded white pebble, likely quartz-rich rock

Most consistent with quartzite or milky-quartz pebble; exact identification requires testing

Dark gray chert or flint nodule

Microcrystalline quartz (SiO₂), commonly chalcedony/quartz

Yellow Chert (Jasper)

Microcrystalline Quartz (SiO2)

Granite Glacial Erratic

Intrusive Phaneritic Felsic Rock (Granite)

Peridotite

Peridotite (varieties include Dunite, Lherzolite, Harzburgite)

Sodalite

Na8(Al6Si6O24)Cl2

Jasper and Quartz conglomerate (River Rock)

Silicon Dioxide (SiO2) - Chalcedony and Quartz variety

Serpentine

Antigorite/Chrysotile/Lizardite (Mg,Fe)3Si2O5(OH)4

Weathered sandstone or limestone fragment

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

Sandstone (with Feldspathic/Arkose qualities)

Arenite (primarily SiO2 with KAlSi3O8 components)

Chert (and Flint variant)

Microcrystalline Quartz (SiO2)

Jasper

Silicon dioxide (SiO2)

Tumbled jasper, likely red/brown jasper

Microcrystalline quartz (chalcedony), SiO₂, colored by iron oxides

Sandstone (with vugs or solution cavities)

Arenite (primarily Quartz and Feldspar with CaCO3 or SiO2 cement)

Serpentinite

Serpentinite (composed primarily of Serpentine group minerals like Antigorite, Lizardite, and Chrysotile)

Chert (containing Flint and Calcareous inclusions)

Silicon Dioxide (SiO2) with Calcium Carbonate (CaCO3) impurities

Quartzite

Quartzite (SiO2)

Limestone (Weathered Pebble)

Calcium Carbonate (CaCO3) / Limestone

Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Weathered limestone

Calcite-rich carbonate rock (mostly CaCO₃), possibly fossiliferous limestone

Chert (Jasper/Limonitic Chert)

Silicon dioxide (SiO2)

Quartz geode

Microcrystalline and crystalline quartz (SiO₂), likely chalcedony-lined geode

Biotite granite pebble

Granite, chiefly quartz (SiO₂), feldspar, and biotite mica

Sandstone (Ferruginous)

Arenite with Iron Oxide cement

Jasper

Silicon Dioxide (SiO2) with iron oxide inclusions

Weathered granitic rock fragment

Likely granite or granodiorite, composed mainly of quartz, feldspar, and mica

Basalt

Basalt (Mafic volcanic rock)

Sapphire

Corundum (Al₂O₃) with trace elements causing color variations.

Bivalve Fossil

Bivalvia (Phylum Mollusca)

Chert (Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Milky Quartz (Water-worn Pebble)

Silicon Dioxide (SiO2)

Fossilized ammonite (likely weathered ammonite cross-section)

Ammonoidea; commonly Jurassic–Cretaceous ammonite fossils replaced by calcite or aragonite