Obsidian
Volcanic Glass (Amorphous Silicon Dioxide)
Category
Browse industrial byproduct (often mistaken for obsidian or mineral) specimens identified by the Rock Identifier community.
Obsidian
Volcanic Glass (Amorphous Silicon Dioxide)
Obsidian
Obsidian (Volcanic Glass, SiO2 + impurities)
Obsidian
Obsidian (Amorphous volcanic glass)
Obsidian
Obsidian (Volcanic Glass)
Sandstone Concretion
Clastic Sedimentary Concretion (typically Quartz/Silica with Iron Oxide)
Ironstone Concretion (Siderite Nodules)
Siderite (FeCO3) in Mudstone or Sandstone matrix
Orange Calcite
Calcite (Calcium Carbonate, CaCO3)
Satin Spar Selenite
Satin Spar (Calcium Sulfate Dihydrate, CaSO4·2H2O)
Pyrite (Fool's Gold)
Iron Disulfide (FeS2)
Concretion
Septarian concretion (likely containing Calcite or Siderite)
Auriferous Quartz or Pyritic Ore
Iron Pyrite (FeS2) or Native Gold (Au) in Matrix
Black tumbled stone, possibly obsidian
Volcanic glass; primarily SiO₂, if obsidian
Obsidian
Volcanic glass
Apache Tear
Obsidian (Hydrated Volcanic Glass - SiO2)
Milky Quartz
Quartz (Silicon Dioxide, SiO2)
Orange Quartz (Ferruginous Quartz)
Silicon Dioxide (SiO2) with Iron Oxide inclusions
Quartz (Iron-stained)
Silicon Dioxide (SiO2)
Dendritic Opal (Merlinite)
Hydrated Silica with Manganese/Iron oxide inclusions (SiO2·nH2O)
Chrysoprase
Silicon dioxide (SiO2) with nickel impurities
Obsidian
Obsidian (Volcanic Glass)
Obsidian
Amorphous volcanic glass (principally SiO2)
Obsidian
Obsidian (Volcanic Glass, SiO2 + impurities)
Obsidian
Volcanic Glass (Primary composition: SiO2 - Silicon Dioxide)
Citrine (Yellow Quartz)
Silicon Dioxide (SiO2)
Iron Nodule
Iron-manganese concretion (Fe-Mn hydroxide)
Sodalite
Sodalite (Na8(Al6Si6O24)Cl2)
Sodalite
Na8(Al6Si6O24)Cl2
Fossil Coral / Bryozoan
Anthozoa or Bryozoa indet. (Calcite/Silica)
Goethite Concretion
Goethite (FeO(OH))
Ferruginous Sandstone (Ironstone Conglomerate fragments)
Ferruginous clastic sedimentary rock (SiO2 cemented by Fe2O3)
Blue Dumortierite in Quartz
Al7(BO3)(SiO4)3O3 (Dumortierite)
Blue Apatite
Fluorapatite (Ca5(PO4)3F)
Obsidian
Obsidian (Volcanic Glass)
Obsidian
Volcanic Glass (SiO2)
Obsidian
Obsidian (Volcanic Glass)
Obsidian
Amorphous volcanic glass (primarily SiO2)
Obsidian
Obsidian (Volcanic Glass)
Obsidian
Obsidian (volcanic glass), predominantly Silicon Dioxide (SiO2)
Black Spinel
Magnesium Aluminum Oxide (MgAl2O4)
Sodalite
Sodalite (Na8(Al6Si6O24)Cl2)
Mahogany Obsidian
Volcanic Glass (SiO2 + Fe2O3)
Obsidian
Volcanic Glass (Amorphous Silica)