Rounded weathered rock, likely basalt or andesite
Fine-grained mafic to intermediate volcanic rock; precise identification requires testing
igneous
Category
Igneous Rock (Volcanic Glass)
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Basalt
Extrusive Igneous Rock
igneous
Limonite Stained Basalt
Hydrated Iron Oxide on Mafic Volcanic Rock (FeO(OH)·nH2O)
igneous
Fine-grained dark igneous rock, likely basalt
Basalt, composed chiefly of plagioclase feldspar and pyroxene, with possible olivine or magnetite
igneous
Olivine-rich Basalt with Peridotite Xenoliths
Porphyritic Basalt containing Dunite/Peridotite (Mg,Fe)2SiO4
igneous
Scoria (vesicular volcanic rock)
Basaltic scoria; chiefly plagioclase, pyroxene, olivine, and volcanic glass
igneous
Polished dark stone, likely basalt
Basalt; chiefly plagioclase feldspar, pyroxene, and commonly olivine
igneous
Rounded dark river pebble, likely basalt
Basalt; fine-grained mafic volcanic rock composed mainly of plagioclase and pyroxene, commonly with olivine
igneous
Polished basaltic rock, likely basalt
Basalt; chiefly plagioclase feldspar, pyroxene, and commonly olivine or magnetite
igneous
Granite-like weathered rock
Felsic intrusive igneous rock, likely granitic or granodioritic
igneous
Vesicular volcanic rock (likely pumice)
Pumice, a highly vesicular volcanic glass, commonly rhyolitic to dacitic in composition
igneous
Obsidian (likely snowflake-free black volcanic glass)
Volcanic glass; predominantly rhyolitic silica melt (SiO₂-rich, noncrystalline)
igneous
Scoria (Lava Rock)
Scoria (Extrusive Igneous Rock)
igneous
Tumbled dark quartzite or basalt pebble
Likely fine-grained basalt (plagioclase–pyroxene), though quartzite is possible from the image
igneous
Snowflake Obsidian
Vitreous volcanic silicate rock (SiO2) with Spherulite inclusions
igneous
Quartz Vein in Host Rock (Breccia/Rhyolite)
Silicon Dioxide (SiO2) with matrix
Mineral in Igneous/Sedimentary host
Basalt with Quartz Vein
Mafic Igneous Rock (SiO2 filling)
igneous
Basalt River Cobble
Basalt (Mafic Igneous Rock)
igneous
Basalt
Extrusive mafic igneous rock
igneous
Likely weathered quartz-rich pebble
Uncertain; possibly granite or quartz-bearing volcanic rock
igneous
Black Obsidian
Volcanic Glass (predominantly SiO2, Silicon Dioxide)
igneous
Vesicular Basalt or Porphyritic Rhyolite
Extrusive Igneous Rock
igneous
Basalt
Extrusive Igneous Rock
igneous
Basalt
Extrusive Igneous Rock
igneous
Basalt
Extrusive igneous rock
igneous
Basalt Pebble
Extrusive Igneous Rock
igneous
Basalt Pebble
Extrusive Igneous Rock
igneous
Basalt
Extrusive Igneous Rock
igneous
Basalt Pebble
Extrusive Igneous Rock
igneous
Basalt Pebble (Shaped)
Extrusive Igneous Rock
igneous
Basalt Fragment
Extrusive Igneous Rock
igneous
Basalt
Extrusive igneous rock
igneous
Basalt
Extrusive Igneous Rock
igneous
Gray volcanic rock, likely basalt
Basalt; primarily plagioclase feldspar, pyroxene, and minor olivine/iron oxides
igneous
Quartz Vein in Host Rock
Silicon Dioxide (SiO2) in matrix
mineral/igneous
Basalt River Stone
Aphanitic Mafic Igneous Rock
igneous
Mica (Biotite or Phlogopite variety)
Phyllosilicate (complex mineral formula involving K, Mg, Fe, Al, Si, and O)
mineral
Leopard Skin Jasper
Orbicular Jasper (Silicon Dioxide, SiO2)
sedimentary
Scoria (vesicular basalt)
Basaltic scoria; predominantly plagioclase, pyroxene, olivine, and volcanic glass
igneous
Olivine in Basalt matrix
Peridotite (Mg, Fe)2SiO4
igneous
Weathered granite or granitic gneiss
Coarse-grained quartz–feldspar–mica rock; likely granite, possibly gneiss
igneous
Basalt
Extrusive Igneous Rock
igneous