Industrial Byproduct (Anthropogenic Rock Like Material)

Possible fossilized shell or fossil fragment

Indeterminate; possibly a small brachiopod or gastropod fossil in mineralized matrix

Bauxite

Bauxite (Mixture of Al(OH)3, AlO(OH), and Fe2O3)

Red Sandstone

Arenite (with Iron Oxide / Hematite cementation)

Chert (Iron-stained)

Microcrystalline Quartz (SiO2)

Sandstone (Quartz-rich)

Clastic sedimentary rock (SiO2 primary)

Ferruginous Sandstone

Clastic Sedimentary Rock (Sandstone with Iron Oxide cement)

Chalcanthite

Hydrated copper(II) sulfate (CuSO4·5H2O)

Iron meteorite fragment

Fe-Ni meteorite, likely an iron meteorite or stony-iron fragment

Pumice (specifically a water-worn, weathered variety)

Vesicular volcanic glass

Basalt

Basalt (Mafic volcanic rock)

Chert Arrowhead

Microcrystalline Quartz (SiO2)

Ironstone (likely Limonite or Goethite)

Ferruginous sedimentary rock (FeO(OH)·nH2O)

Likely metallic meteorite fragment

Undetermined; possibly an iron meteorite or stony-iron meteorite

Quartz Pebble

Silicon Dioxide (SiO2)

Chert (Yellow Jasper)

Cryptocrystalline Quartz (SiO2)

Possible basalt or iron-rich slag-like geological specimen

Basalt (tentative); predominantly plagioclase and pyroxene, possibly with magnetite/iron oxides

Fossilized bivalve shell

Recrystallized calcium-carbonate shell, commonly fossil oyster or clam (Bivalvia)

Sandstone (Ferruginous)

Arenite (with Iron Oxide cement)

Small gray rock fragment

Indeterminate; possibly quartz-rich granite, chert, or concrete-like silicate material

Polished brown jasper (likely picture jasper)

Microcrystalline quartz/chalcedony, SiO₂, with iron-oxide and clay inclusions

Orbicular jasper (likely brecciated jasper)

Microcrystalline quartz/chalcedony (SiO₂) with iron-oxide and silica-rich clasts

Basalt

Basalt (Mafic Extrusive Igneous Rock)

Sea Glass

Man-made silicate glass weathering product

Chert Arrowhead

Cryptocrystalline Quartz (SiO2)

Chert Arrowhead (Projectile Point)

Microcrystalline Quartz (Chert or Flint)

Reddish iron-rich pebble, possibly jasper or altered basalt

Likely hematite/goethite-bearing basalt or ferruginous jasper; exact identification requires testing

Basalt

Basalt (Mafic volcanic rock)

Red Sandstone

Arenite (Iron-rich Sandstone)

Polished brecciated jasper (likely ocean jasper or orbicular jasper)

Microcrystalline quartz/chalcedony (SiO₂) with iron-oxide and other mineral inclusions

Iron-rich concretion or slag-like rock

Goethite–hematite limonite concretion, possibly iron slag

Porphyritic Basalt

Basalt (Mafic Extrusive Igneous Rock)

Peridotite

Peridotite (varieties include Dunite, Lherzolite, Harzburgite)

Transit Token (RTD Denver)

Nickel-plated brass or bronze alloy (Cu-Sn-Zn-Ni)

Limestone (Weathered)

Sedimentary Carbonate Rock (CaCO3)

Chert (Yellow Jasper/Flint)

Silicon dioxide (SiO2) - Cryptocrystalline Quartz

Fossilized bivalve shell fragment

Pectinid or related scallop bivalve; shell originally composed mainly of calcite (CaCO₃)

Milky quartz (rough fragment)

Quartz, silicon dioxide (SiO₂)

Red Sandstone

Arenite (Fe2O3 rich)

Chert (specifically Jasper/Flint)

Microcrystalline Quartz (SiO2)

Blue glass-like bead or gemstone keychain ornament

Indeterminate; likely cobalt-blue glass or synthetic blue spinel, not identifiable as a natural mineral from the image

Gravel or Crushed Stone

Fragmented Aggregate Stone

Polished orbicular jasper (likely ocean jasper)

Siliceous microcrystalline quartz/chalcedony aggregate; commonly sold as Ocean Jasper