Industrial Byproduct (Anthropogenic Rock Like Material)

Chert Arrowhead

Microcrystalline Quartz (SiO2)

Sandstone (Ferruginous)

Arenite (with Iron Oxide cement)

Basalt

Basalt (Mafic volcanic rock)

Chert (Yellow Jasper)

Cryptocrystalline Quartz (SiO2)

Iron-rich concretion or slag-like rock

Goethite–hematite limonite concretion, possibly iron slag

Fossilized bivalve shell

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

Polished brown jasper (likely picture jasper)

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

Porphyritic Basalt

Basalt (Mafic Extrusive Igneous Rock)

Chert Arrowhead

Cryptocrystalline Quartz (SiO2)

Orbicular jasper (likely brecciated jasper)

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

Common opal (rough opalized material)

Hydrated amorphous silica, SiO₂·nH₂O; likely common opal with dark mineral inclusions

Reddish iron-rich pebble, possibly jasper or altered basalt

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

Likely metallic meteorite fragment

Undetermined; possibly an iron meteorite or stony-iron meteorite

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

Transit Token (RTD Denver)

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

Likely beach-worn pebbles

Lithified rock fragments; exact rock type cannot be determined from the photo

Peridotite

Peridotite (varieties include Dunite, Lherzolite, Harzburgite)

Chert (Yellow Jasper/Flint)

Silicon dioxide (SiO2) - Cryptocrystalline Quartz

Sea Glass

Amorphous Silica (Anthropogenic glass) - SiO2

Milky quartz (rough fragment)

Quartz, silicon dioxide (SiO₂)

Limestone (Weathered)

Sedimentary Carbonate Rock (CaCO3)

Chert Arrowhead (Projectile Point)

Microcrystalline Quartz (Chert or Flint)

Fossilized bivalve shell fragment

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

Red Sandstone

Arenite (Fe2O3 rich)

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

Diamond (or Diamond Simulant)

C (Carbon) or synthetic equivalent

Andesite

Andesite (Intermediate Extrusive Volcanic Rock)

Polished brecciated jasper

Microcrystalline quartz (SiO₂), with iron-oxide staining

Chert (specifically Jasper/Flint)

Microcrystalline Quartz (SiO2)

Small dark rock fragment (not identifiable from the image)

Undetermined; no diagnostic mineral features are visible

Yellow Ochre / Limonite

Limonite (FeO(OH)·nH2O)

Jasper (Red Jasper)

Silicon Dioxide (SiO₂)

Chert (specifically Flint or Gray Chalcedony)

Microcrystalline Quartz (SiO2)

Milky Quartz or Calcite Pebble

Silicon Dioxide (SiO2) or Calcium Carbonate (CaCO3)

Polished orbicular jasper (likely ocean jasper)

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

Chert (and Flint variant)

Microcrystalline Quartz (SiO2)

Siltstone or Fine-grained Sandstone pebble

Siltstone (primarily SiO2 with clay minerals)

Polymictic conglomerate (possibly impact breccia)

Lithified polymictic conglomerate/breccia; clasts appear mainly mafic volcanic rock, with quartz- or feldspar-rich fragments in a dark matrix

Chert (Flint)

Chert (SiO2)

Obsidian-like volcanic rock (likely basaltic volcanic glass)

Basaltic obsidian or tachylite; composition chiefly volcanic glass with plagioclase and pyroxene

Concrete Rubble with Aggregate

Hardened Portland Cement Paste with Coarse Aggregate