Not A Rock (Man Made Origin)

Mixed polished gemstone and mineral collection

Primarily quartz varieties (SiO₂), plus probable aventurine, rose quartz, amethyst, agate, jasper, serpentine, feldspar, and possibly dyed or man-made glass pieces

Turquoise

Hydrous phosphate of copper and aluminium (CuAl6(PO4)4(OH)8·4H2O)

Asphalt (Bituminous Concrete)

Bituminous Concrete / Pavement

Weathered granite or granitic gneiss pebble

Granite: quartz + feldspar + mica; possibly weakly foliated gneiss

Red Coral

Corallium rubrum

Chert (Flint / Quartz Nodule)

Microcrystalline Quartz (SiO2)

Sandstone Pebble

Ferruginous Sandstone (SiO2 with Fe2O3)

Granite (Polished Countertop Surface)

Plutonic Igneous Rock (Felsic)

Small tumbled dark stone, possibly sodalite or blue-gray jasper

Undetermined from the image; visual appearance is consistent with sodalite-bearing rock or jasper

Quartz-rich rock, likely milky quartz or quartzite

Quartz (SiO₂), possibly in a quartzite or hydrothermal vein matrix

Quartzite

Metamorphic Rock (Mainly SiO2)

Granite (rounded cobble)

Granite; chiefly quartz, potassium feldspar, plagioclase, and mica

Sandstone

Arenite (SiO2 based clastic rock)

Small dark mineral/rock fragment

Indeterminate; possibly magnetite-bearing basalt or iron-rich slag

Quartz-rich rock, likely milky quartz or quartzite

Quartz (SiO₂), possibly quartzite if metamorphically recrystallized

Sandstone

Sedimentary Rock (Quartz Sandstone)

Pink Granite

Felsic Intrusive Igneous Rock (composed primarily of K-Feldspar, Quartz, and Mica)

Quartz-rich rock, likely milky quartz vein material

Predominantly quartz (SiO₂); exact rock type cannot be confirmed from the photograph

Unidentified gray metallic object

Not determinable from the image; likely a metal screw or manufactured fastener rather than geological material

Bauxite

Bauxite (Al(OH)3, γ-AlO(OH), and α-AlO(OH))

Likely weathered limestone or calcareous tuff

Calcite-rich carbonate rock, chiefly CaCO₃; exact identification is uncertain from the image

Cowrie shell

Marine gastropod shell; likely a cowrie (family Cypraeidae), species not identifiable from the image

Blue-green opal, likely polished common or synthetic opal

Opal (hydrated amorphous silica, SiO₂·nH₂O); identification from the image is uncertain

Granite

Phaneritic Felsic Igneous Rock

Granite

Granite (Plutonic Igneous Rock)

Granite

Granite (Felsic Plutonic Rock)

Chert (specifically Tan/Gray Chert)

Microcrystalline quartz (SiO2)

Weathered quartz-rich rock, possibly quartzite or quartz vein fragment

Quartzite (mostly microcrystalline SiO₂), identification uncertain from image

Shungite

Fullerene-bearing carbonaceous rock

Mixed rounded river gravel

Polymictic alluvial gravel; likely mixtures of quartzite, granite, basalt, sandstone, and other silicate rocks

Banded Gneiss

Gneiss (Foliated Metamorphic Rock)

Likely weathered mafic rock (basalt or gabbro)

Basalt–gabbroic rock; chiefly plagioclase feldspar, pyroxene, and possibly olivine

Dark gray rock fragment (tentative basalt or slate)

Indeterminate; possibly fine-grained basalt, or metamorphic slate

Chert (Flint)

Silicon Dioxide (SiO2)

Red Sandstone

Arenite (Ferruginous Sandstone)

Basaltic rock fragment (likely vesicular basalt)

Basalt; chiefly plagioclase, pyroxene, and possibly olivine

Eroded Brick or Pumice-like Scoria

Vesicular Basalt / Scoria (Anthropogenic variant: Eroded Firebrick)

Sandstone (with potential Arkose/Lithic characteristics)

Arenite (Sedimentary rock composed of sand-sized grains)

Uncertain dark, weathered rock fragment

Possibly basalt or a dark mafic volcanic rock; identification is limited by blur and lighting

Tumbled quartz-rich carbonate rock

Likely massive quartz (SiO₂), possibly calcite-bearing marble or limestone

Chert

Silicon dioxide (SiO2)

Porphyry

Porphyritic Igneous Rock