Not A Rock (Synthetic Material)

Sandstone

Arenite (primarily SiO2)

Sandstone

Arenite (SiO2 based with quartz grains)

Shale

Laminated Mudstone

Sandstone

Arenite (primarily SiO2)

Red Sandstone

Arenite (primarily SiO2 with Fe2O3)

Quartz / Common Agate

Silicon Dioxide (SiO2)

Sandstone with Desert Varnish

Arenite with Ferromanganese patina

Sandstone

Arenite (SiO2 principal)

Sandstone

Arenite

Sandstone (Wonderstone)

Clastic Sedimentary Rock (primarily SiO2)

Red Sandstone

Arenite (Ferruginous Sandstone)

Unidentified dark, flat specimen

Indeterminate; image resolution is insufficient for mineral identification

Weathered quartz-bearing rock

Quartz-rich vein material; likely quartz with iron oxides and feldspar, exact rock type uncertain

River Pebble (Quartz/Jasper)

Silicon Dioxide (SiO2)

Shale (with Iron Staining)

Argillaceous mudstone / Shale

Ruby

Corundum (mineral species), variety: Ruby (Al2O3 with Cr3+ as the chromophore)

Milky quartz with dark mineral veins

Quartz, silicon dioxide (SiO₂), likely massive vein quartz; dark veins may be chlorite, mica, iron/manganese oxides, or a sulfide mineral

Sandstone

Arenite

Azurite-Malachite (often a mixed specimen)

Azurite: Cu3(CO3)2(OH)2; Malachite: Cu2(CO3)(OH)2. The specimen appears to be a natural mixture or intergrowth of these two minerals.

Eroded volcanic rock formation (likely basalt)

Basalt, a fine-grained mafic volcanic rock composed mainly of plagioclase feldspar and pyroxene, with possible olivine

Red Sandstone

Arenite (with Iron Oxide cement)

Basalt (Vesicular)

Extrusive mafic igneous rock; primarily (Mg, Fe)2SiO4 (Olivine), CaAl2Si2O8 (Plagioclase Feldspar), and Pyroxene

Coarse-grained gray metamorphic rock, likely gneiss

Biotite–quartz–feldspar gneiss (probable)

Gneiss

Gneissic Metamorphic Rock

Sandstone (Tumbled/River Pebble)

Arenite (composed primarily of SiO2)

Breciated Limestone with Calcite Veins

Sedimentary Breccia (CaCO3)

Diorite (River Cobble)

Intermediate phaneritic igneous rock

Quartz (Milky Quartz)

Silicon Dioxide (SiO2)

Sandstone

Arenite

Natural turquoise-bearing rock

Turquoise, CuAl₆(PO₄)₄(OH)₈·4H₂O, likely in a limonite or host-rock matrix

Quartz-rich foliated rock, possibly milky quartz vein material

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

Serpentinite

Serpentinite (composed primarily of Serpentine group minerals (Mg,Fe,Ni,Al,Zn,Mn)2-3(Si,Al,Fe)2O5(OH)4)

Petrified Wood

Fossilized wood / Silicified wood

Sandstone

Arenite (SiO2 based)

Sandstone

Arenite (composed primarily of SiO2)

Vesicular volcanic rock (likely scoria)

Scoria, a vesicular basaltic to andesitic volcanic rock

Possible dark cobble or pebble

Unidentified rock; composition cannot be determined from the image

Unidentified dark rock fragment

Likely basalt or fine-grained mafic rock; exact identification is uncertain from the photograph

Asphalt aggregate

Human-made bituminous asphalt containing crushed silicate rock aggregate

Likely quartz-rich rock fragment

Indeterminate; possibly quartz-bearing granite or quartzite

Quartz-bearing granite or pegmatitic rock

Granite, composed mainly of quartz, feldspar, and mica; exact identification is uncertain from the image

Iron-stained quartz vein rock

Quartz-rich rock with iron-oxide/hydroxide coatings (hematite/goethite); exact host rock undetermined