Not A Rock (Synthetic Material)

Fossiliferous Limestone (Coquina / Shell Limestone)

Biogenic Limestone (Calcium Carbonate, CaCO3)

Chert (specifically Yellow or River Chert)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Slate

Slate (Metamorphic Rock)

Vesicular basalt (likely weathered lava rock)

Basalt, predominantly calcium-rich plagioclase, pyroxene, and commonly olivine; vesicular texture from gas bubbles

Dark metamorphic rock, likely biotite schist or gneiss

Quartz–feldspar–biotite metamorphic rock; exact identification requires a fresh surface and testing

Quartzite

Quartzite (SiO2)

Red Sandstone

Ferruginous Sandstone (SiO2 with Iron Oxide impurities)

Weathered quartz-rich metamorphic rock, possibly quartzite

Quartzite; predominantly quartz (SiO₂), with minor feldspar, mica, and iron-oxide staining

Weathered quartz-rich rock, likely quartzite

Quartzite; predominantly crystalline SiO₂, possibly iron-oxide stained

Chert / Jasper

Microcrystalline Quartz (SiO2)

Sandstone (Ferruginous)

Clastic sedimentary rock (primarily SiO2 with Fe2O3 cement)

Red Sandstone

Sandstone (lithic arenite / ferruginous sandstone)

Amethyst Geode

Amethyst (Silicon Dioxide), Formula: SiO2

Tumbled carnelian agate

Cryptocrystalline quartz (SiO₂), chalcedony variety with iron-oxide coloration

Porphyritic polymictic breccia (likely volcanic breccia)

Volcanic breccia; probable polymictic andesite–dacite breccia with quartz/feldspar clasts

Sandstone (Ferruginous)

Arenite (primarily SiO2 with Fe2O3 cement)

Quartzite

Quartzite (SiO2)

Quartzite Pebble

Quartzite (SiO2)

Tumbled red jasper

Jasper, an opaque microcrystalline variety of quartz (SiO₂), colored mainly by iron oxides

Fossilized Gastropod in Limestone

Gastropoda (Class) in Fossiliferous Limestone

Snowflake Obsidian (or similar porphyritic volcanic rock)

Obsidian with Spherulites (if glassy), or Porphyritic Rhyolite/Andesite (if crystalline groundmass)

Polished orbicular jasper (likely ocean jasper)

Silicified volcanic rock; chiefly microcrystalline quartz (SiO₂), with feldspar and iron-rich alteration minerals

Pink Granite

Felsic Plutonic Rock (primarily Quartz, Potassium Feldspar, and Plagioclase)

Blue sodalite beads

Sodalite, Na₈(Al₆Si₆O₂₄)Cl₂

Weathered iron-rich rock, possibly laterite or limonite-bearing stone

Hydrated iron oxides/hydroxides, chiefly limonite-goethite mixture; exact identification requires testing

Banded Iron Formation (Jasper / Hematite Ore)

Banded Iron Formation (BIF) / Hematite-Quartz Rock

Ferruginous Sandstone

Clastic Sedimentary Rock (Sandstone with Iron Oxide cement)

Sandstone (with Iron Staining)

Clastic sedimentary rock (High Silica / Iron Oxide)

Limestone

Sedimentary rock composed primarily of Calcium Carbonate (CaCO3)

Chert (Jasper)

Microcrystalline Quartz (SiO2) with hematite impurities

Granite pebble

Granite, typically quartz–feldspar–mica aggregate

Bloodstone

Heliotrope (cryptocrystalline Quartz, SiO2 with inclusions of Hematite)

Pumice

Pumice (Volcanic Rock / Glass Foam)

Chalcedony (Botryoidal or Agate nodule)

Silicon Dioxide (SiO2)

Chert / Flint

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Quartz Geode

Crystalline Silicon Dioxide (SiO2) in a Geode

Quartz Mica Schist

Mica-Quartz Schist (Chemical: SiO2 + KAl2(AlSi3O10)(OH)2)

Tumbled serpentine

Serpentinite; chiefly serpentine-group minerals, Mg3Si2O5(OH)4

Weathered sandstone or iron-stained siltstone

Quartz-rich clastic sedimentary rock, likely ferruginous sandstone

Granite

Granite

Polished red jasper

Jasper, microcrystalline quartz (SiO₂) colored by iron oxides

Sandstone (Ferruginous)

Arenite (Fe-rich)