Obsidian
Volcanic Glass (predominantly SiO2 – Silicon Dioxide, but non-crystalline)
Category
Browse industrial byproduct (often mistaken for obsidian or mineral) specimens identified by the Rock Identifier community.
Obsidian
Volcanic Glass (predominantly SiO2 – Silicon Dioxide, but non-crystalline)
Obsidian
Obsidian (Volcanic glass, primarily SiO2)
Black Obsidian
Obsidian, volcanic glass (Amorphous SiO₂)
Sulfur (with Matrix)
Native Sulfur (S8)
Slag
Ferrous slag (by-product of iron smelting)
Obsidian
Obsidian (Volcanic Glass)
Quartz (Iron-Stained Quartz Pebble)
Silicon Dioxide (SiO2)
Ferruginous Quartz (Iron-stained Quartz)
Silicon Dioxide (SiO2) with Hematite/Goethite inclusions
Obsidian
Obsidian (volcanic glass; primarily SiO2)
Quartzite
Quartzite (SiO2)
Obsidian
Obsidian (Volcanic Glass)
Vesicular Basalt
Extrusive Mafic Igneous Rock (Vesicular Basalt)
Arfvedsonite (often mistakenly sold as Astrophyllite)
Arfvedsonite [Na3(Fe2+)4Fe3+Si8O22(OH)2]
Dumortierite Quartz
Dumortierite (Al7BO3(SiO4)3O3 / inclusion in SiO2)
Quartzite
Quartzite (composed primarily of silica, SiO2)
Obsidian
Obsidian (volcanic glass), predominantly amorphous SiO₂
Obsidian
Volcanic Glass (Primary composition: SiO2 - Silicon Dioxide)
Obsidian
Obsidian
Chert (with Manganese Dendrites)
Chert (Cryptocrystalline Quartz, SiO2)
Concrete / Conglomerate (Man-made)
Artificial Conglomerate (Cementitious Composite)
Obsidian
Volcanic Glass (SiO2 - Silicon Dioxide with impurities)
Obsidian
Obsidian (Volcanic Glass, SiO2 + impurity)
Black Obsidian
Volcanic Glass (predominantly SiO2)
Quartz (Milky/River Quartz)
Silicon Dioxide (SiO2)
Obsidian
Obsidian (Volcanic Glass)
Opalite
Man-made synthetic glass with opalescent effects (SiO2 + metal oxides)
Obsidian
Volcanic Glass (predominantly SiO2)
Mahogany Obsidian
Volcanic Glass with Hematite/Magnetite inclusions
Chalcopyrite
Chalcopyrite (CuFeS2)
Ironstone Concretion (Limonite/Goethite)
Ferruginous concretion (Fe2O3·nH2O)
White Quartzite
Quartzite (primarily SiO2 - Silicon Dioxide)
Sodalite-rich Syenite (Sunset Sodalite)
Sodalite-Syenite (Na8[Al6Si6O24]Cl2 with KAlSi3O8)
Pyrite (on Quartz matrix)
Iron Disulfide (FeS2)
Obsidian
Obsidian (Volcanic Glass, SiO2)
Quartzite
Quartzite (SiO2)
Obsidian
Volcanic Glass (predominantly SiO2)
Quartzite
Quartzite (SiO2)
Obsidian
Obsidian (principally SiO2 with MgO and Fe3O4)
Mahogany Obsidian
Volcanic Glass with Hematite/Magnetite (SiO2 + Fe2O3)
Carborundum
Silicon Carbide (SiC)
Quartzite Pebble
Quartzite (SiO2 with minor impurities)
Sandstone (with Iron Siderite Concretion)
Arenite with Ironstone Concretion (FeCO3)