Igneous Rock (Volcanic Glass)

Snowflake Obsidian

Spherulitic Volcanic Glass (primarily SiO2 with Cristobalite inclusions)

Likely vesicular basalt (scoria)

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

Tumbled basalt (probable)

Basalt, a fine-grained mafic volcanic rock composed mainly of plagioclase and pyroxene, commonly with olivine and iron oxides

Snowflake Obsidian

Volcanic glass containing Spherulitic Cristobalite (SiO2)

Vesicular volcanic rock, likely scoria

Scoria; basaltic to andesitic volcanic rock, mainly plagioclase, pyroxene, and volcanic glass

Apache Tears (Obsidian)

Volcanic Glass (SiO2 - Silicon Dioxide with impurities)

Apache Tear

Obsidian (Hydrated Silica Rich Volcanic Glass)

Apache Tear

Obsidian (Hydrated Volcanic Glass) - SiO2 (with impurities)

Vesicular volcanic rock, likely scoria

Scoria; typically basaltic to andesitic composition, chiefly plagioclase, pyroxene, and volcanic glass

Weathered rhyolitic tuff or altered volcanic rock

Felsic volcanic tuff, likely devitrified or hydrothermally altered

Quartz Druzy (on Geode Fragments)

Silicon Dioxide (SiO2)

Weathered mafic rock, likely basalt

Basalt; primarily plagioclase feldspar, pyroxene, and minor olivine or iron oxides

Rounded gray pebble, likely basalt or andesite

Fine-grained mafic to intermediate volcanic rock; commonly basalt (plagioclase ± pyroxene/olivine)

Weathered volcanic rock, likely andesite or basalt

Fine-grained mafic to intermediate volcanic rock; commonly plagioclase ± pyroxene, amphibole, and iron oxides

Basalt River Stone

Basaltic Igneous Rock

Porphyritic Basalt or Porphyritic Andesite

Porphyritic Igneous Rock

Weathered basalt or andesite

Fine-grained volcanic rock, likely basaltic-andesite; chiefly plagioclase feldspar, pyroxene, and possibly olivine or volcanic glass

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

White Agate

SiO2 (Microcrystalline Quartz)

Vesicular volcanic rock, likely scoria

Scoria; predominantly basaltic composition (plagioclase, pyroxene, olivine, and volcanic glass)

Red scoria (vesicular volcanic rock)

Scoria, typically basaltic to andesitic volcanic rock

Pumice

Highly vesicular volcanic rock, commonly rhyolitic to dacitic glass (SiO₂-rich volcanic material)

Basalt Pebble

Extrusive Igneous Rock (Mafic)

Obsidian

Obsidian (volcanic glass), amorphous SiO2 + impurities

Volcanic Breccia

Pyroclastic breccia

Xenolith in Basalt

Mafic Igneous Rock with Felsic Inclusion

Mahogany Obsidian

Volcanic Glass (with inclusions of Magnetite or Hematite)

Porphyritic basaltic-andesite cobble

Fine-grained plagioclase–pyroxene volcanic rock, likely basaltic andesite

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Weathered volcanic rock, likely basalt

Basalt; commonly composed of plagioclase, pyroxene, and iron-rich oxides

Chalcedony (Grey/White Agate)

Silicon Dioxide (SiO₂)

Weathered vesicular volcanic rock, likely basaltic scoria

Vesicular basalt/scoria; mainly plagioclase, pyroxene, and iron-rich glass or oxides

Weathered porphyritic volcanic rock

Likely porphyritic andesite or dacite, with plagioclase phenocrysts in a fine-grained volcanic groundmass

Scoriaceous basalt (scoria)

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

Basalt

Mafic extrusive igneous rock

Yellow chalcedony or quartz fragment

Microcrystalline quartz, SiO₂ (tentative; possibly iron-stained chalcedony)

Volcanic Breccia

Pyroclastic Breccia

Scoria (vesicular volcanic rock)

Basaltic scoria; primarily plagioclase, pyroxene, olivine, and volcanic glass

Black Obsidian

Obsidian (Volcanic Glass), primarily SiO2 (Silicon Dioxide)

Pumice (likely basaltic pumice/scoria)

Vesicular volcanic rock, commonly basaltic; mainly plagioclase, pyroxene, and volcanic glass

Basalt Pebble

Extrusive igneous rock

Obsidian-like volcanic glass (likely slag or natural obsidian)

Obsidian, primarily amorphous volcanic silica glass (approximately SiO₂); identification is uncertain from an image