Mahogany Obsidian
Obsidian (Volcanic Glass) with Hematite/Magnetite inclusions
Category
Browse industrial byproduct (often mistaken for obsidian or mineral) specimens identified by the Rock Identifier community.
Mahogany Obsidian
Obsidian (Volcanic Glass) with Hematite/Magnetite inclusions
Milky Quartz with Dendritic Inclusions
Silicon Dioxide (SiO2) with impurities
Black stone bead bracelet
Likely black tourmaline (schorl), though identification is uncertain from the image
Sandstone Concretion
Clastic Sedimentary Concretion (primarily SiO2 with Fe2O3 cement)
Ironstone concretion
Siderite or Limonite-rich Concretion (FeO(OH)·nH2O)
Concretion (Sandstone)
Carbonate-cemented Sandstone Concretion
Obsidian
Volcanic Glass (SiO2 - Silicon Dioxide with impurities)
Banded Sandstone
Arenite (with iron oxide banding)
Black Onyx
Silicon Dioxide (SiO2)
Quartzite River Rock with Dendrites
Metamorphosed Quartz-rich Sandstone with Manganese Oxide (MnO2) inclusions
Obsidian
Volcanic Glass (SiO2)
Obsidian (likely black volcanic glass)
Obsidian; silica-rich, noncrystalline volcanic glass, typically rhyolitic (approximately 70–75% SiO₂)
Iron Concretion
Ferruginous concretion (Fe2O3·nH2O / FeO(OH))
Iron-rich meteorite candidate
Unclassified stony-iron or iron meteorite; possible weathered ordinary chondrite
Blue Dumortierite Quartz
Dumortierite in Quartz (AlAl6BSi3O12(O,OH)3)
Dendritic Limestone
Calcite with Manganese Oxide (Manganese Dendrites)
Sandstone with Liesegang Rings
Clastic Sedimentary Rock with Iron Oxide Precipitates (SiO2 + Fe2O3)
Variscite in Matrix
Variscite (AlPO4 · 2H2O)
Blue Obsidian
Volcanic Glass (SiO2 with inclusions)
Polished tektite (likely indochinite)
Impact glass; natural silica-rich glass, approximately SiO₂ 70–80%
Carved smoky quartz (likely)
Quartz, silicon dioxide (SiO₂), smoky variety
Obsidian
Volcanic Glass (SiO2 rich)
Obsidian
Obsidian (principally SiO2 + MgO, Fe3O4)
Chrysoprase
Chalcedony (Silicon Dioxide, SiO2), flavored by Nickel
Dumortierite Quartz
Al7BO3(SiO4)3O3 (Aluminum borate silicate)
Sodalite
Na8(Al6Si6O24)Cl2
Dendritic Agate
Silicon Dioxide (SiO2) with Manganese/Iron oxide inclusions
Flesh-colored Quartz Mineral
SiO2 (Silicon Dioxide) with Iron Impurities
Arfvedsonite in Quartz
Arfvedsonite [Na3(Fe2+4Fe3+)Si8O22(OH)2] often hosted in Quartz or Feldspar
Snowflake Obsidian
Vitreous volcanic silicate (SiO2 with Cristobalite inclusions)
Black Obsidian
Obsidian (Volcanic Glass), primarily SiO2 (Silicon Dioxide)
Quartz
Silicon Dioxide (SiO2)
Obsidian
Volcanic Glass (SiO2 + minor impurities)
Green Aventurine
Silicon Dioxide (Quartz with Fuchsite inclusions) - SiO2
Coal
Carbonaceous sedimentary rock
Ironstone Concretion
Siderite or Hematite Concretion
Milky Quartz or Calcite Pebble
Silicon Dioxide (SiO2) or Calcium Carbonate (CaCO3)
Black Obsidian
Obsidian, SiO2 (amorphous)
Sandstone Concretion
Ferruginous Sandstone Concretion
Ironstone Concretion
Siderite or Ferruginous Concretion (FeCO3 or Iron Oxides)
Black tourmaline (schorl)
Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
Banded Calcite (often sold as "Peaches and Cream" or "Orange Calcite")
Calcium Carbonate (CaCO3)