Dark volcanic rock, likely basalt
Basalt (fine-grained mafic igneous rock; commonly plagioclase, clinopyroxene, and olivine)
igneous
Category
Igneous Rock (Volcanic Glass)
Browse igneous rock (volcanic glass) specimens identified by the Rock Identifier community.
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Agate
Silicon Dioxide (SiO2)
gemstone
Agate
Silicon Dioxide (Chalcedony), SiO2
gemstone
Pumice
Pumice (felsic volcanic rock)
igneous
Weathered granite fragment
Granite, chiefly quartz, potassium feldspar, plagioclase, and biotite/hornblende
igneous
Weathered vesicular volcanic rock (likely vesicular basalt or scoria)
Vesicular basalt; primarily plagioclase, pyroxene, and iron-rich oxides, with possible glass
igneous
Obsidian
Volcanic Glass (Primary composition: SiO2 - Silicon Dioxide)
igneous
Porphyritic Basalt
Extrusive igneous rock
igneous
Basalt Pebble
Extrusive Igneous Rock
igneous
Obsidian
Obsidian (Volcanic Glass; SiO2 content > 70%)
igneous
Granite fragment
Granite, a coarse-grained felsic intrusive igneous rock composed mainly of quartz, feldspar, and mica
igneous
Tumbled gray pebble, likely basalt or dark chert
Most consistent with fine-grained basalt (plagioclase–pyroxene), though gray chert (microcrystalline SiO₂) is possible
igneous
Weathered dark-gray pebble
Likely basalt or a basaltic volcanic rock; exact identification requires testing
igneous
Basalt Pebble
Extrusive Igneous Rock
igneous
Weathered mafic rock (probable basalt or gabbro fragment)
Basalt–gabbroic rock; chiefly plagioclase feldspar and pyroxene, possibly olivine
igneous
Greenstone (Chert)
Microcrystalline Silica (SiO2) with chlorite/epidote inclusions
metamorphic
Basalt (Polished)
Extrusive mafic igneous rock
igneous
Basalt (River Stone)
Extrusive mafic igneous rock
igneous
Brecciated jasper (likely ocean jasper or rhyolitic jasper)
Silica-rich volcanic breccia composed mainly of microcrystalline quartz/chalcedony (SiO₂), with iron-oxide staining and possible feldspar
igneous
Vesicular basalt (likely scoria)
Vesicular basalt; chiefly plagioclase, pyroxene, and iron-rich minerals
igneous
Vesicular volcanic rock, likely pumice or scoriaceous rhyolite
Pumice/scoria; predominantly silicate glass with quartz–feldspar minerals
igneous
Basalt
Mafic extrusive igneous rock
igneous
Weathered mafic rock, likely basalt
Basalt; predominantly plagioclase feldspar and pyroxene, possibly olivine and iron oxides
igneous
Basalt (River Stone)
Extrusive mafic igneous rock
igneous
Polished/tumbled stone, likely mahogany obsidian
Obsidian, natural volcanic glass (composition typically rhyolitic)
igneous
Tumbled blue-gray stone, likely basalt
Basalt (fine-grained mafic volcanic rock; chiefly plagioclase and pyroxene, commonly with magnetite)
igneous
Obsidian
Volcanic Glass (SiO2 - Silicon Dioxide with impurities)
Igneous
Eroded volcanic rock formation (likely basalt)
Basalt, a fine-grained mafic volcanic rock composed mainly of plagioclase feldspar and pyroxene, with possible olivine
igneous
Scoria (vesicular basalt)
Basaltic scoria; predominantly plagioclase, pyroxene, olivine, and volcanic glass
igneous
Basalt
Extrusive igneous rock
igneous
Basalt
Extrusive Igneous Rock
igneous
Basalt
Extrusive Igneous Rock
igneous
Basalt
Extrusive igneous rock
igneous
Basalt
Extrusive igneous rock
igneous
Basalt
Extrusive Igneous Rock
igneous
Basalt
Extrusive igneous rock
igneous
Basalt
Extrusive Igneous Rock
igneous
Basalt
Extrusive igneous rock
igneous
Basalt
Extrusive igneous rock
igneous
Basalt
Extrusive Igneous Rock
igneous
Basalt
Extrusive igneous rock
igneous
Rhyolite
Extrusive igneous rock
igneous