Non Geological

River Pebble (Greywacke or Quartzite-rich Sandstone)

Lithic Sandstone (primarily SiO2 with rock fragments)

Limonite Pseudomorph after Pyrite

Limonite (Hydrous iron oxides, FeO(OH)·nH2O) replacing Pyrite (FeS2)

Black Obsidian

Obsidian (Volcanic Glass, ~70% SiO2)

Beaded gemstone bracelet, likely amethyst and mixed polished stones

Amethyst: quartz (SiO₂); other beads appear to be assorted quartz/chalcedony or jasper

Snowflake Obsidian

Spherulitic Volcanic Glass (primarily SiO2)

Tumbled pink-and-cream stone, possibly pink opal

Likely common opal (hydrated amorphous silica, SiO₂·nH₂O); identification is uncertain from the photo

Small weathered pebble, possibly limestone

Indeterminate carbonate-rich rock; likely calcite-bearing limestone

Dark metamorphic rock, likely biotite schist or gneiss

Quartz–feldspar–biotite metamorphic rock; exact identification requires a fresh surface and testing

Obsidian

Volcanic glass (SiO2 + impurities)

Polished carnelian agate

Chalcedony, microcrystalline quartz (SiO₂), with iron-oxide color bands

Quartz (Iron-stained)

Silicon Dioxide (SiO2)

Polished agate geode slice

Microcrystalline quartz (chalcedony), SiO₂

Likely ironstone or ferruginous sandstone fragment

Iron-oxide-cemented sandstone; commonly quartz grains cemented by hematite/goethite (composition cannot be confirmed from the image)

Quartzite

Metamorphic Quartzite (SiO2)

Snowflake Obsidian

Obsidian with Cristobalite inclusions (mostly amorphous SiO2)

Obsidian

Obsidian (Volcanic Glass)

Obsidian

Volcanic Glass (SiO2 + impurities)

Green glass sphere/marble

Soda-lime glass (primarily SiO2, Na2O, CaO)

Synthetic Resin / Plastic Figurine

Synthetic Polymer (Copolymer of Polyethylene or Resin)

Obsidian

Volcanic glass (primary composition: SiO2)

Black Obsidian

Obsidian (Volcanic glass), 70–75% SiO2

Gemstone bead necklace, likely mixed tourmaline and quartz

Probable schorl/dravite tourmaline with quartz or smoky quartz; exact identification requires testing

Polished brecciated jasper

Silicified microcrystalline quartz (SiO₂), commonly called brecciated or ocean jasper

Obsidian Arrowhead

Volcanic Glass (predominantly SiO2)

Obsidian

Volcanic Glass (Amorphous SiO2-rich glass)

Black Obsidian

Obsidian (Volcanic Glass)

Quartzite

Quartzite (SiO2)

Limestone

Calcium Carbonate (CaCO3)

Rounded river pebble, likely basalt or andesite

Fine-grained mafic to intermediate volcanic rock; exact identification requires testing

Siltstone or Fine-grained Sandstone pebble

Siltstone (primarily SiO2 with clay minerals)

Obsidian

Volcanic Glass

Quartzite

Quartzite (primarily SiO2)

Obsidian

Volcanic Glass (SiO2)

Bull Quartz (Milky Quartz)

Silicon Dioxide (SiO2)

Quartzite

Quartzite (primarily SiO2)

Common opal (rough opalized material)

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

Botryoidal chalcedony/geode fragment

Microcrystalline quartz, SiO₂, likely chalcedony with drusy quartz

Quartzite

Quartzite (chiefly SiO2)

Polished Black Obsidian

Volcanic Glass (70-75% SiO2)

Obsidian

Volcanic Glass (SiO2)

Beaded blue-and-green gemstone jewelry

Likely dyed or treated chalcedony/agate and green aventurine or glass-like stone; exact identification requires testing

Anthracite Coal

Anthracite