Basalt

Dark, fine-grained rock fragment (possibly basalt)

Basalt, a plagioclase–pyroxene volcanic rock; identification is uncertain from the photo

Basalt with Mineral Vein (Cobble)

Basalt (with likely Quartz/Calcite vein)

Dark fine-grained stone pebble

Possibly basalt; identification is uncertain from the small, distant image

Vesicular basalt (likely weathered scoria)

Mafic volcanic rock; chiefly plagioclase, pyroxene, and often olivine, with abundant gas vesicles

Copper-bearing Basalt with Epidote and Quartz

Native copper in basalt amygdaloidal matrix

Vesicular basalt (scoria-like volcanic rock)

Basalt, a mafic volcanic rock composed mainly of plagioclase feldspar, pyroxene, and minor olivine

Gabbro

Gabbro (mafic intrusive igneous rock)

Gabbro (Water-worn Pebble)

Gabbro

Rounded gray pebble, likely basalt or andesite

Fine-grained volcanic rock, probably basaltic-andesite; exact identification requires testing

Basalt

Basalt (Mafic volcanic rock)

Basalt

Extrusive mafic igneous rock

Basalt Pebble

Basalt (Mafic Extrusive Igneous Rock)

Black basalt or dark volcanic rock fragment

Likely basalt, composed chiefly of plagioclase feldspar and pyroxene, with possible magnetite

Vesicular Basalt River Rock

Vesicular Basalt

Vesicular Basalt

Extrusive mafic igneous rock (Basalt with vesicular texture)

Basalt with Quartz Vein

Mafic Igneous Rock (SiO2 filling)

Basalt

Aphanitic Mafic Igneous Rock

Basalt (likely vesicular basalt)

Basalt; chiefly plagioclase feldspar, pyroxene, and commonly olivine

Basalt (likely vesicular basalt)

Basalt; chiefly plagioclase feldspar, pyroxene, and often olivine

Basalt

Mafic volcanic rock (various silicate minerals)

Basalt

Mafic Fine-Grained Igneous Rock

Rounded dark speckled pebble, likely basalt

Basalt; fine-grained mafic volcanic rock, typically composed of plagioclase, clinopyroxene, and iron-magnesium minerals

Veined basalt (likely basalt with quartz/calcite vein)

Basalt, aphanitic mafic volcanic rock; vein minerals likely quartz (SiO₂) or calcite (CaCO₃)

Polished black pebble, likely basalt

Basalt (fine-grained mafic volcanic rock; visual identification is uncertain)

Vesicular basalt (possibly scoriaceous basalt)

Basalt; chiefly plagioclase, pyroxene, and olivine, with iron oxides

Gabbro

Gabbro (Mafic Intrusive Igneous Rock)

Gabbro

Gabbro (mafic intrusive igneous rock)

Vesicular Basalt

Aphanitic Mafic Volcanic Rock

Basalt

Extrusive Igneous Rock (Mafic)

Basalt

Basalt (primarily composed of Plagioclase feldspar and Pyroxene)

Basalt

Basalt (Mafic volcanic rock)

Dark gray crystalline rock, possibly basalt

Basalt (tentative; plagioclase–pyroxene–iron oxide assemblage)

Basalt with Amygdule

Aphanitic Mafic Volcanic Rock (Basalt) with Zeolite/Quartz Infill

Rounded gray pebble, likely basalt

Basalt; fine-grained mafic volcanic rock, chiefly plagioclase and pyroxene with possible olivine

Basalt with Plagioclase Feldspar

Basalt (mafic extrusive igneous rock) with plagioclase feldspar phenocrysts

Basalt

Basalt (composition of plagioclase feldspar and pyroxene)

Basalt

Basalt (Mafic Extrusive Igneous Rock)

Vesicular basalt (scoriaceous basalt)

Basalt, chiefly plagioclase feldspar and pyroxene with minor olivine; vesicles formed by trapped volcanic gas

Probable rough basalt or mafic igneous fragment

Fine-grained basalt, likely plagioclase–pyroxene–olivine aggregate

Basalt

Mafic Igneous Rock (composed primarily of Pyroxene and Plagioclase Feldspar)

Basalt

Basalt (Mafic Extrusive Igneous Rock)

Basalt

Mafic volcanic rock (primarily plagioclase feldspar and pyroxene)