Not A Rock (Synthetic Material)

Black obsidian (probable)

Volcanic glass; primarily SiO₂-rich rhyolitic composition

Weathered quartz-rich pebble, possibly milky quartz or chalcedony

Quartz, SiO₂; exact variety uncertain from the image

Peridot (Olivine)

Olivine (Magnesium Iron Silicate), (Mg,Fe)2SiO4

Chert (Jasper)

Chert / Microcrystalline Quartz (SiO2)

Chert with Quartz Veining

Silicon Dioxide (SiO2)

Flint / Chert Nodules in Limestone

Cryptocrystalline Quartz (SiO2) within Carbonate Rock

Jasper

Jasper (Silicon Dioxide, SiO2)

Uncertain polymict breccia or altered volcanic rock

Likely hydrothermally altered volcanic breccia; exact mineral identification requires testing

Rounded river or beach pebble

Likely quartz-rich sandstone or quartzite; exact identification requires a close-grained view and hardness test

Granite pebble

Granite; chiefly quartz, potassium feldspar, plagioclase, and minor biotite/hornblende

Sandstone

Arenite (composed primarily of SiO2)

Gemstone Sand (Mineral Assortment)

Mixed Mineral Concentrates (Commonly including Quartz SiO2, Garnet X3Y2(SiO4)3, and Tourmaline (Na,Ca)(Li,Mg,Al)3(Al,Fe,Mn)6(BO3)3(Si6O18)(OH,F)4)

Sandstone Pebble

Arenite (SiO2 primarily)

Milky Quartz

Silicon Dioxide (SiO2)

Sandstone (likely Graywacke or Arkose)

Clastic Sedimentary Rock (primarily SiO2 with various lithic fragments)

Chert (specifically Flint or Jasper variant)

Microcrystalline quartz (SiO2)

Chert (Grey-Green Var.)

Silicon Dioxide (SiO2)

Flagstone (Sandstone)

Clastic Sedimentary Rock (composed of quartz and feldspar)

Red Sandstone with Reduction Spot

Quartzose Sandstone with a Leach/Reduction Spot

Peridotite

Peridotite (Ultramafic Rock)

Chert Pebble

Microcrystalline Quartz (SiO2)

Rounded granite cobble

Granite; chiefly quartz, feldspar, and mica/amphibole

Sandstone (Ferruginous)

Arenite with Iron-Oxide cement

Tumbled jasper (likely brecciated or orbicular jasper)

Microcrystalline quartz (SiO₂), with iron-oxide inclusions

Possible weathered granite or gneiss

Feldspar–quartz–mica rock; exact identification is uncertain from the photograph

Sandstone (Ferruginous)

Arenite (primarily SiO2 with Fe2O3 staining)

Likely basaltic volcanic rock

Basalt, chiefly plagioclase feldspar and clinopyroxene, with possible olivine or iron oxides

Sandstone (Banded)

Clastic Sedimentary Rock (primarily SiO2 with Iron Oxide staining)

Granite Pegmatite with Muscovite Mica

Granite Pegmatite (Silicon Dioxide and complex silicates)

Rounded quartz-rich cobble, likely granite-derived stone

Granite or granitic gneiss, composed mainly of quartz, feldspar, and minor mica

Yellow-brown quartz/chalcedony fragment

Quartz, SiO₂; likely microcrystalline chalcedony with iron-oxide staining

Vesicular basalt

Basalt, typically composed of plagioclase feldspar, pyroxene, and minor olivine or iron oxides

Sandstone

Arenite (SiO2 based)

Sandstone (Ferruginous)

Arenite (with Iron Oxides)

Quartz-rich feldspathic rock, likely granite or granitic gneiss

Granite/granitic gneiss; chiefly quartz (SiO₂), feldspar, and minor mica

Red Sandstone

Arenite (Ferruginous Sandstone)

Travertine

Terrestrial Sedimentary Form of Calcium Carbonate (CaCO3)

Sandstone

Arenite (primarily SiO2)

Mixed rock and mineral collection

Mixed lithologies; likely quartz, feldspar, basalt, granite, chert, sandstone, and metamorphic rocks

Sandstone (Greywacke/Lithic Sandstone)

Arenite / Lithic Sandstone

Basalt

Extrusive mafic igneous rock

Granite Cobble

Phaneritic Felsic Igneous Rock