Black Obsidian
Volcanic Glass (predominantly SiO2)
Category
Browse industrial byproduct (often mistaken for obsidian or mineral) specimens identified by the Rock Identifier community.
Black Obsidian
Volcanic Glass (predominantly SiO2)
Ferruginous Sandstone with Concretion
Sandstone (SiO2 dominated with Fe2O3 cement)
Ferruginous Quartz
Silicon Dioxide (SiO2) with iron oxide inclusions
Ironstone Concretion / Goethite-Hematite Nodule
Goethite/Hematite (α-FeO(OH) / Fe2O3)
Black Obsidian
Volcanic Glass (SiO2 + impurities)
Ironstone Concretion
Limonitic/Hematitic Concretion
Scoria (Basaltic Lava Rock)
Vesicular Basalt
Amazonite
KAlSi3O8 (Potassium Feldspar, variety of Microcline)
Snowflake Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with Cristobalite inclusions)
Pyrite (Fool's Gold)
Iron Sulfide (FeS2)
Sandstone (with manganese staining)
Clastic sedimentary rock (primarily SiO2)
Sodalite
Na8(Al6Si6O24)Cl2
Ironstone Nodule (Ironstone Concretion)
Siderite-rich Mudstone (FeCO3) or Limonite (FeO(OH)·nH2O)
Mixed Mineral Collection
Multi-mineral Assemblage (Quartz, Jasper, Obsidian, Pyrite, etc.)
Blue Apatite
Fluorapatite (Ca5(PO4)3F)
Sandstone (Banded)
Clastic Sedimentary Rock (primarily Quartz, SiO2)
Sodalite
Sodalite - Na8(Al6Si6O24)Cl2
Chrysoprase
Silicon Dioxide (Nickel-bearing Chalcedony) - SiO2
Snowflake Obsidian
Spherulitic Volcanic Glass (SiO2 + impurities)
Ironstone Concretion (Limonite/Goethite)
Iron oxide concretion (contains FeO(OH)·nH2O)
Blue Apatite
Apatite group (Ca5(PO4)3(F,Cl,OH))
Quartzite
Quartzite (SiO2)
Ironstone Concretion
Ferruginous Sandstone / Siderite Concretion
Ironstone Concretion
Siderite or Hematite-bonded Concretion
Black Obsidian
Volcanic Glass (SiO2 + impurities)
Obsidian
Volcanic glass
Obsidian
Volcanic glass
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
Blue Quartzite
Blue Quartzite (Primary mineral: Quartz, SiO2 with magnesio-riebeckite or crocidolite inclusions)
Ironstone concretion / Limonitic Sandstone
Goethite/Hematite Cemented Sandstone (Hydrated Iron Oxide)
Pyrite (Fool's Gold)
Iron Disulfide (FeS2)
Liesegang Banded Sandstone (Wonderstone)
Ferruginous Sandstone with Liesegang Rings
Basalt
Basalt
Chert / Chalcedony
Silicon Dioxide (SiO2)
Green Aventurine (Green Quartzite)
Silicon Dioxide (SiO2) with inclusions of Fuchsite (K(Al,Cr)2(AlSi3O10)(OH)2)
Jasper with Manganese Dendrites
Silicon Dioxide (SiO2) with Oxide Mineral Inclusions
Ferruginous Quartz
Silicon Dioxide (SiO2) with Hematite/Limonite impurities
Black Obsidian
Obsidian (Volcanic Glass)
Pyrite in Shale
Iron Sulfide (FeS2)
Black Star Diopside (beads)
Diopside (CaMgSi2O6) - a member of the pyroxene group
Greenstone
Greenschist (primarily composed of chlorite, actinolite, and epidote)
Obsidian
Volcanic Glass (SiO2)