Tektite (Natural Glass)

Blue Glass or Slag Glass

Amorphous Silica (Anthropogenic Glass)

Petoskey Stone

Hexagonaria percarinata (Silicified/Calcitic)

Sea Glass

Amorphous silicon dioxide (Man-made glass weathered by nature)

Black Obsidian

Obsidian (Amorphous Silicon Dioxide)

Likely slag or metallic industrial byproduct

Unidentified iron-rich ferrous slag; possibly magnetite-bearing slag

Amethyst

Quartz (Silicon Dioxide, SiO2)

Dyed Agate Geode Slice

Silicon Dioxide (SiO2) - Banded Chalcedony

Red Jasper

Jasper (Silicate Mineral), SiO2 with Fe2O3 inclusions

Quartz-rich granite or granitic pebble

Granite; primarily quartz (SiO₂), potassium feldspar, plagioclase, and minor mica/iron oxides

Polished Basalt

Basalt (Mafic volcanic rock)

Rounded granite cobble

Granite; chiefly quartz, feldspar, and mica/amphibole

Colorless faceted gemstone, likely cubic zirconia

Cubic zirconia (synthetic ZrO₂), possibly glass or white sapphire

Obsidian (likely black volcanic glass)

Obsidian; naturally occurring rhyolitic glass, primarily SiO₂

Red Coral

Corallium rubrum (Calcium Carbonate, CaCO3)

Blue calcite (likely)

Calcite, CaCO₃

Polished dark pebble, likely basalt

Basalt, chiefly plagioclase feldspar and pyroxene, with possible olivine or magnetite

Snowflake Obsidian (Polished Cabochon)

Obsidian with Spherulitic Cristobalite (SiO2)

Snowflake Obsidian

Volcanic glass with Spherulite inclusions (SiO2)

Red jasper (tumbled river pebble)

Jasper, an opaque microcrystalline variety of quartz/chalcedony (SiO₂), colored mainly by iron oxides

Obsidian

Volcanic Glass

Tumbled greenstone/chlorite-rich pebble

Likely chlorite-rich greenschist or altered basalt; exact identification requires testing

Obsidian

Volcanic Glass (SiO2 - Silicon Dioxide with impurities)

Citrine Quartz

Silicon dioxide (SiO2)

Obsidian

Vitreous volcanic silicate (70-75% SiO2)

Red Quartz (Tumbled)

Silicon Dioxide with Iron Oxide inclusions (SiO2)

Vesicular Basalt

Vesicular Basalt (Mafic Volcanic Rock)

Polished pink-and-white quartz bead bracelet

Quartz (SiO₂), likely rose quartz and milky quartz; some orange beads may be iron-stained quartz or pale carnelian

Blue Goldstone

Man-made glass with crystalline copper/cobalt inclusions

Obsidian

Volcanic Glass (Amorphous Silicon Dioxide)

Iron-rich vesicular rock, possibly slag or weathered basalt

Identification uncertain; likely ferruginous basalt/ironstone, with possible anthropogenic iron slag

Obsidian (likely mahogany or black obsidian)

Volcanic glass; chiefly amorphous SiO₂-rich rhyolitic composition

Obsidian

Volcanic Glass

Man-made Slag (Industrial Byproduct)

Anthropogenic Glassy Residue

Blue Quartzite (Dyed Quartzite)

Silicon Dioxide (SiO2) with dye

Citrine

Silicon Dioxide (SiO2) with iron impurities

Tumbled yellow jasper or serpentine

Jasper: microcrystalline quartz (SiO₂); possible serpentine: Mg₃Si₂O₅(OH)₄

Vesicular Basalt (Scoria)

Mafic Igneous Volcanic Rock

Smelter Slag

Anthropogenic Silicate Slag

Obsidian

Volcanic Glass (SiO2)

Yellow Quartz (Citrine or Quartzite Pebble)

Silicon Dioxide (SiO2)

Likely vesicular basalt (scoria)

Basaltic scoria; chiefly plagioclase, pyroxene, and olivine with vesicles

Polished/tumbled brown jasper or iron-rich chert

Microcrystalline quartz (SiO₂), commonly colored by hematite/goethite