Not A Rock (Synthetic Material)

Red Sandstone

Sandstone (Quartz Arenite / Arkose with Hematite cement)

Fossil Snail

Gastropoda fossil

Bowling Ball (Brunswick T-Zone Deep Space)

Polyester resin / Polyurethane polymer

Tumbled Black Stone

Unknown (possibly basalt, obsidian, or black jasper)

Milky quartz with dark host-rock inclusions

Quartz (SiO₂), likely in a granitic or metamorphic matrix

Concrete / Conglomerate (Man-made)

Artificial Conglomerate (Cementitious Composite)

Milky Quartz with Chlorite/Amphibite Inclusions

Silicon Dioxide (SiO2) with various mineral inclusions

Jasper (likely brecciated or chalcedony-rich jasper)

Microcrystalline quartz/chalcedony, SiO₂, with iron-oxide impurities

Serpentinite (often called Jade or Nephrite substitute)

Serpentinite (composed primarily of Antigorite, Lizardite, or Chrysotile)

Blue quartz (likely dyed or synthetic-treated quartz beads)

Quartz, silicon dioxide (SiO₂)

Sandstone

Arenite (Clastic Sedimentary Rock)

Polished dark agate or jasper specimen

Cryptocrystalline quartz (chalcedony), SiO₂; exact identification is uncertain from the image

Rounded gray river pebble

Likely quartz-rich metamorphic or igneous pebble; exact identification requires testing

Sandstone

Arenite (SiO2 composed primarily of quartz)

Chert

Silicon dioxide (SiO2)

Slag (Industrial Byproduct)

Artificial silicate/iron byproduct

Polished turquoise-like stone

Likely turquoise, hydrated copper–aluminum phosphate: CuAl₆(PO₄)₄(OH)₈·4H₂O; identification is uncertain from the photo

Sandstone

Sedimentary Clastic Rock

Iron-stained quartz-bearing rock

Quartz (SiO₂), likely with limonite/goethite iron oxides and possibly feldspar

Quartzite (probable)

Quartzite; predominantly recrystallized quartz (SiO₂)

Sandstone

Clastic sedimentary rock

Sandstone (Tumbled / Rounded)

Sedimentary Rock (Quartz arenite)

River Stone (likely Quartzite or Limestone)

Silicon dioxide (SiO2) or Calcium carbonate (CaCO3)

Small weathered mineral/rock fragment

Unidentified; likely quartz-rich material, possibly quartzite or feldspar-bearing rock

Coquina

Coquina (Bioclastic Limestone)

Sandstone

Arenite (SiO2 dominant)

Iron-rich sandstone concretion

Ferruginous sandstone, cemented chiefly by iron oxides (such as goethite and hematite)

Sandstone

Sedimentary Rock (Quartz arenite)

Granitic Gneiss Pebble

Gneiss (felsic metamorphic rock)

Gneiss

Gneiss (a rock type, not a specific mineral with a formula)

Granite Pebble

Felsic Igneous Rock (Granitic composition)

Siltstone

Siltstone (composed of microscopic quartz and clay minerals)

Conglomerate

Conglomerate (Sedimentary Clastic Rock)

Serpentine

Serpentine group ((Mg,Fe,Ni,Al,Zn,Mn)3(Si,Al)2O5(OH)4)

Likely fossil oyster shell

Fossilized bivalve shell; exact species cannot be identified from the image

Crushed Granite / Landscaping Gravel

Granitoid

Tumbled brown stone, possibly chert or iron-stained quartzite

Indeterminate from photograph; possible microcrystalline quartz (SiO₂)

Limestone (Weathered Aggregate)

Sedimentary Carbonate Rock (CaCO3)

Sandstone

Arenite (primarily Quartz-rich)

Sandstone

Arenite (SiO2 primarily)

Blue-gray stone pebble (possibly slag or a weathered rock)

Unidentified fine-grained rock; composition cannot be determined from the image

Rounded yellow-brown cobble

Likely weathered sandstone or quartz-rich conglomeratic clast; exact identification requires a fresh surface and testing