Basalt with Olivine Phenocrysts
Porphyritic Basalt (Mineral formula of Olivine: (Mg,Fe)2SiO4)
Igneous
Category
Igneous Rock (Volcanic Glass)
Browse igneous rock (volcanic glass) specimens identified by the Rock Identifier community.
Amethyst
Silicon Dioxide (SiO2) with iron impurities
mineral
Clear Quartz (Druzy)
Crystalline Silicon Dioxide (SiO2)
mineral
Yellow Jasper
Silicon Dioxide (SiO2) with Goethite/Limonite inclusions
sedimentary
Petrified Wood
Silicified Wood (SiO2)
metamorphic
Red Jasper
Silicon Dioxide (SiO2) with Hematite impurities
sedimentary
Olivine-bearing Basalt / Scoria
Mafic Igneous Rock (primarily (Mg, Fe)2SiO4)
igneous
Quartz / Rock Crystal
Silicon Dioxide (SiO2)
mineral
Chalcedony (Agate)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
mineral
Picture Jasper
Silicified sedimentary or volcanic rock (primarily SiO2)
sedimentary
Granodiorite Pebble
Granodiorite (containing Quartz, Plagioclase Feldspar, and Biotite/Amphibole)
igneous
Clear Quartz
Silicon Dioxide (SiO2)
mineral
Milky Quartz (Druzy Geode fragment)
Silicon Dioxide (SiO2)
mineral
Clear Quartz crystals on a Matrix base (Geode fragment)
Silicon Dioxide (SiO2)
mineral
Clear Quartz
Silicon Dioxide (SiO2)
mineral
Quartz Vein Rock
Silicon Dioxide (SiO2)
Mineral
Greenstone (Amygdaloidal Basalt)
Amygdaloidal Basalt (frequently composed of Plagioclase Feldspar, Pyroxene, and Olivine with Chlorite inclusions)
igneous
Clear Quartz (Druzy/Crystal Cluster)
Silicon Dioxide (SiO2)
mineral
Quartz (Clear Quartz/Rock Crystal)
Silicon Dioxide (SiO2)
mineral
Obsidian
Volcanic glass (SiO2 - Silicon dioxide predominant composition)
Igneous
Red Rhyolite Porphyry
Rhyolite (Porphyritic texture)
igneous
Quartz Vein in Host Rock
Silicon Dioxide (SiO2) within Metasedimentary or Igneous matrix
mineral
Apache Tear
Obsidian (Hydrated Volcanic Glass - SiO2)
igneous
Snowflake Obsidian
Obsidian (volcanic glass) with Cristobalite inclusions
igneous
Obsidian Arrowhead
Volcanic Glass (Primary composition: SiO2)
igneous
Mixed Mineral Specimens
Mixed Silicates, Oxides, and Phosphates (SiO₂, Ca₅(PO₄)₃(F,Cl,OH), Na₈Al₆Si₆O₂₄Cl₂, etc.)
mineral
Quartz (Druzy or Crystalline variety)
Silicon Dioxide (SiO2)
mineral
River Cobble (likely Basalt or Chert)
Siliceous River Rock / Microcrystalline Quartz / Mafic Igneous
igneous/sedimentary
Mahogany Obsidian
Volcanic Glass with Hematite/Magnetite inclusions
igneous
Obsidian
Volcanic Glass (Primary component: SiO2)
igneous
Obsidian / Chert (Arrowhead Artifact)
Obsidian (volcanic glass, SiO2 with impurities)
igneous
Obsidian (Apache Tear)
Amorphous Volcanic Glass (SiO2 + impurities)
igneous
Obsidian
Obsidian (Volcanic Glass, SiO2 + impurities)
igneous
Apache Tear
Hydrated Obsidian (Natural Volcanic Glass)
igneous
Apache Tear (Obsidian)
Volcanic glass (SiO2 - Silicon Dioxide)
igneous
Obsidian (Gold Sheen)
Obsidian (SiO2 + impurities)
igneous
Pyrite (Fool's Gold)
Iron Sulfide (FeS2)
mineral
Granite Pebble
Felsic Intrusive Igneous Rock (composed of Quartz, Alkali Feldspar, and Plagioclase)
igneous
Milky Quartz
Crystalline Silicon Dioxide (SiO2)
mineral
Chalcedony with inclusions (Agate/Quartz)
Silicon Dioxide (SiO2)
mineral
Granite
Granite (Felsic Plutonic Rock)
igneous
Basalt
Extrusive Mafic Igneous Rock (composed primarily of Plagioclase, Pyroxene, and Olivine)
igneous