Volcanic Glass (Igneous)

Obsidian Arrowhead

Volcanic Glass (70% or more SiO2)

Obsidian

Obsidian (Volcanic Glass, SiO2 + impurities)

Apache Tear (Obsidian)

Hydrated volcanic glass (SiO2 with inclusions)

Obsidian

Volcanic glass (SiO2 - Silicon Dioxide)

Obsidian

Obsidian (Volcanic Glass, primarily SiO2)

Mahogany Obsidian

Volcanic Glass with Hematite/Magnetite inclusions

Apache Tear (Obsidian)

Volcanic glass (SiO2 - Silicon Dioxide)

Pumice

Highly vesicular volcanic rock, typically rhyolitic to dacitic; chiefly volcanic glass with feldspar, quartz, and minor mafic minerals

Vesicular basalt (likely scoria or weathered pumice)

Vesicular basalt; chiefly plagioclase, pyroxene, olivine, and volcanic glass

Pumice

Pumice (Silicic volcanic glass with vesicular structure)

Obsidian

Obsidian (Volcanic glass), SiO2 (70% or more)

Obsidian

Obsidian (Volcanic Glass) SiO2 (70% or more)

Yellow-green faceted gemstone (possibly peridot)

Undetermined; peridot is gem-quality olivine, (Mg,Fe)₂SiO₄

Pumice

Pumice (Vesicular Felsic Igneous Rock)

Vesicular volcanic rock, likely pumice or scoria

Pumice/scoria; predominantly volcanic glass with plagioclase, pyroxene, and/or olivine

Pumice (with oxidation)

Pumice (Vitreous pyroclastic rock)

Obsidian (Black)

Obsidian (approx. 70–75% SiO2)

Porphyritic basalt with quartz or feldspar phenocrysts

Basaltic rock; likely vesicular/porphyritic basalt, with pale mineral inclusions possibly quartz, feldspar, or calcite

Polished black stone pendant, likely obsidian

Volcanic glass; primarily silica-rich rhyolitic glass (SiO₂), if obsidian

Pumice

Pumice (Vesicular volcanic glass / Rhyolite or Trachyte)

Black tumbled stone, possibly obsidian

Obsidian (volcanic glass), likely; identification uncertain from the image

Obsidian

Volcanic glass (SiO2-rich extrusive igneous rock)

Black Obsidian

Volcanic Glass (Amorphous Silicon Dioxide, SiO2)

Obsidian

Volcanic Glass (Extrusive Igneous Rock, primarily SiO2)

Scoriaceous basalt (scoria)

Vesicular basalt; primarily plagioclase, pyroxene, olivine, and volcanic glass

Obsidian

Volcanic Glass (High silica amorphous rock)

Pumice

Vesicular Felsic Extrusive Igneous Rock

Vesicular volcanic rock, likely pumice

Pumice; highly vesicular volcanic glass, commonly rhyolitic to dacitic in composition

Tumbled mahogany obsidian

Volcanic glass; primarily SiO₂ with iron-oxide-rich brown inclusions

Pumice

Pumice (volcanic glass formed of highly vesicular rough textured rock)

Amethyst

Silicon dioxide (variant with ferric iron impurities), SiO2

Possible vesicular basalt or scoriaceous volcanic rock

Basaltic scoria; chiefly plagioclase, pyroxene, and olivine with volcanic glass

Likely obsidian fragment

Volcanic glass, predominantly silica-rich rhyolitic composition (SiO₂-rich)

Chalcedony (specifically Agate and Carnelian variety)

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

Chalcedony (Agate/Quartz)

Silicon Dioxide (SiO2)

Pumice

Pumice

Tumbled black stone, likely basalt or obsidian

Uncertain; likely fine-grained basalt (plagioclase–pyroxene) or dark volcanic glass (obsidian)

Obsidian

Volcanic Glass (Primary composition: SiO2 - Silicon Dioxide)

Mahogany Obsidian

Volcanic glass (SiO2 with Hematite or Magnetite inclusions)

Likely weathered basalt or andesite fragment

Fine-grained mafic to intermediate volcanic rock; commonly plagioclase ± pyroxene ± olivine

Vesicular volcanic rock, likely pumice or scoria

Pumice (highly vesicular rhyolitic–andesitic volcanic glass) or scoria (vesicular basaltic–andesitic rock)

Porphyritic basaltic-andesite cobble

Porphyritic andesite to basaltic andesite; plagioclase-rich volcanic rock