Igneous Rock (Volcanic Glass)

Vesicular basalt (probable)

Basalt; chiefly plagioclase feldspar, clinopyroxene, and iron-rich minerals, with vesicles possibly lined by zeolites or calcite

Basalt Pebble

Extrusive Igneous Rock

Basalt Pebble

Extrusive Igneous Rock

Tumbled basalt pebble

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

Pumice

Pumice (a volcanic glass, primarily SiO2 with Al2O3)

Chalcedony (Agate)

Silicon Dioxide (SiO2)

Basalt with Quartz Vein

Basalt with silicon dioxide (SiO2) inclusion

Red Scoria

Scoria (Vesicular Basalt)

Vesicular basalt (scoria-like lava rock)

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

Vesicular Basalt (Lava Rock)

Vesicular Basalt

Tumbled rhyolite (likely)

Rhyolite, a felsic volcanic rock composed mainly of quartz and alkali feldspar, with biotite or hornblende

Basalt

Basalt (Mafic volcanic rock)

Likely polished rhyolite or porphyritic volcanic rock

Rhyolite, possibly flow-banded or altered rhyolite; composition mainly quartz and alkali feldspar with minor biotite/iron oxides

Rhyolite (likely porphyritic)

Rhyolite; chiefly quartz, alkali feldspar, plagioclase, and volcanic glass, with possible iron-oxide staining

Vesicular volcanic rock, likely pumice or scoria

Pumice/scoria; predominantly silica-rich volcanic glass with feldspar and possible quartz or mafic minerals

Dark, coarse-grained igneous rock, likely basalt or gabbro

Basalt (fine-grained) or gabbro (coarse-grained), composed mainly of plagioclase feldspar and pyroxene

Basalt (Water-worn)

Aphanitic Mafic Igneous Rock

Dark gray-brown stone, likely basalt or fine-grained volcanic rock

Basalt (tentative; likely plagioclase–pyroxene rock)

Weathered basalt pebble

Basalt, a fine-grained mafic volcanic rock; likely olivine- and pyroxene-bearing

Rounded volcanic rock, likely basaltic andesite

Fine- to medium-grained mafic volcanic rock; probable basalt or basaltic andesite

Pink-orange quartz-rich rock, likely rhyolite or jasper

Probable rhyolite (microcrystalline quartz and feldspar), possibly jasper/chalcedony

Vesicular basalt (likely scoria)

Basaltic volcanic rock; primarily plagioclase, clinopyroxene, olivine, and volcanic glass

Likely vesicular basalt (scoria-like fragment)

Basaltic volcanic rock; chiefly plagioclase, clinopyroxene, olivine, and volcanic glass

Fine-grained gray rock, likely andesite or basalt

Aphanitic volcanic rock; probable basaltic-andesite (plagioclase ± pyroxene, minor iron oxides)

Likely reddish granite/porphyritic igneous rock fragments

Feldspar–quartz–mica aggregate, possibly pink granite or rhyolite

Vesicular volcanic rock, likely pumice or scoriaceous rhyolite

Pumice/scoria; predominantly silica-rich volcanic glass with feldspar and quartz crystallites

Pumice

Extrusive volcanic rock (Vesicular Rhyolite/Dacite/Andesite)

Basalt

Extrusive Igneous Rock

Obsidian (Arrowhead Lithic Tool)

Obsidian (Amorphous Volcanic Glass / SiO2 + inclusions)

Eroded volcanic rock formation (likely basalt)

Basalt, a fine-grained mafic volcanic rock composed mainly of plagioclase feldspar and pyroxene, with possible olivine

Greenstone (Chert)

Microcrystalline Silica (SiO2) with chlorite/epidote inclusions

Basalt Pebble

Extrusive Igneous Rock

Pumice or Vesicular Basalt/Scoria (water-worn)

Vesicular volcanic rock

Quartz Vein in Host Rock

Silicon Dioxide (SiO2) within Metasedimentary or Igneous Matrix

Basalt

Mafic extrusive igneous rock

Weathered granite fragment

Granite, chiefly quartz, potassium feldspar, plagioclase, and biotite/hornblende

Basalt (River Pebble)

Extrusive Mafic Igneous Rock

Basalt (River Pebble)

Extrusive mafic igneous rock

Basalt (River Pebble)

Extrusive mafic igneous rock

Basalt

Basalt (Mafic igneous rock)

Quartz on Host Rock

Silicon Dioxide (SiO2)

Dark volcanic rock, likely basalt

Basalt (fine-grained mafic igneous rock; commonly plagioclase, clinopyroxene, and olivine)