Igneous Rock (Volcanic Glass)

Likely weathered quartz-rich pebble

Uncertain; possibly granite or quartz-bearing volcanic rock

Amethyst-rich vesicular volcanic rock (probable amethyst basalt/scoria)

Quartz (SiO₂) in vesicular basaltic volcanic rock; precise identification requires testing

Polished dark stone sphere, likely black obsidian

Obsidian (natural volcanic glass; composition varies, commonly rhyolitic)

Fine-grained dark gray rock, likely basalt

Basalt; chiefly plagioclase feldspar, pyroxene, and commonly olivine or iron oxides

Pumice

Highly vesicular volcanic glass (unnamed scientific variant: Rhyolitic/Andesitic Pumice)

Likely basalt (possibly weathered volcanic rock)

Basalt; predominantly plagioclase feldspar and pyroxene, with possible olivine and iron oxides

Basalt (Vesicular Basalt / Scoria)

Vesicular Basalt

Dark, vesicular volcanic rock (probable basaltic scoria)

Basaltic scoria; mainly plagioclase, clinopyroxene, olivine, and volcanic glass

Polished dark stone, likely basalt

Basalt; chiefly plagioclase feldspar, pyroxene, and commonly olivine

Banded Basalt with Sandstone Vein

Basalt with sedimentary intrusion

Limonite Stained Basalt

Hydrated Iron Oxide on Mafic Volcanic Rock (FeO(OH)·nH2O)

Pumice

Vesicular Rhyolite or Dacite

Scoria (Lava Rock)

Scoria (Extrusive Igneous Rock)

Rounded dark mafic cobble, likely basalt

Basalt; primarily plagioclase feldspar, clinopyroxene, and commonly olivine or magnetite

Likely vesicular volcanic rock (scoriaceous basalt)

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

Vesicular basalt (likely weathered volcanic scoria)

Basalt; chiefly plagioclase, clinopyroxene, olivine, and volcanic glass

Basalt River Cobble

Basalt (Mafic Igneous Rock)

Basalt

Extrusive mafic igneous rock

Gray volcanic rock, likely basalt

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

Polished black stone, possibly basalt or black jasper

Basalt (fine-grained mafic rock) or microcrystalline quartz if jasper

Basalt (likely vesicular basalt)

Basalt; primarily plagioclase feldspar, clinopyroxene, and olivine, with iron-titanium oxides

Likely weathered basalt or iron-rich volcanic rock

Basalt; primarily plagioclase feldspar, pyroxene, and iron-rich oxides

Granite-like weathered rock

Felsic intrusive igneous rock, likely granitic or granodioritic

Agate

Silicon Dioxide (Chalcedony), SiO2

River Stone (Basalt)

Extrusive Igneous Rock (Mafic)

Basalt River Stone

Aphanitic Mafic Igneous Rock

Likely polished/tumbled dark mineral or glassy rock fragment

Indeterminate from image; possibly hornblende, schorl tourmaline, or obsidian

Rounded dark river pebble, likely basalt

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

Basalt with Quartz Vein

Mafic Igneous Rock (SiO2 filling)

Porphyritic Basalt or Porphyritic Andesite

Porphyritic volcanic rock

Vesicular basalt (likely weathered basaltic rock)

Basalt; predominantly plagioclase, clinopyroxene, olivine, and volcanic glass

Fine-grained dark igneous rock, likely basalt

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

Tumbled dark quartzite or basalt pebble

Likely fine-grained basalt (plagioclase–pyroxene), though quartzite is possible from the image

Weathered granite or granitic gneiss

Coarse-grained quartz–feldspar–mica rock; likely granite, possibly gneiss

Agate

Silicon dioxide (Chalcedony), SiO2

Agate

Silicon dioxide (chalcedony), SiO2

Agate

Silicon Dioxide (Chalcedony), SiO2

Agate

Silicon dioxide (SiO2)

Agate

Silicon dioxide (SiO2)

Basalt

Extrusive igneous rock

Red vesicular volcanic rock, likely scoria

Scoria (vesicular basalt/andesite), composed mainly of plagioclase, pyroxene, and iron-rich glass

Agate

Silicon dioxide (chalcedony), SiO2