Obsidian
Volcanic Glass (SiO2 + impurities)
Category
Browse sedimentary (or mineraloid) specimens identified by the Rock Identifier community.
Obsidian
Volcanic Glass (SiO2 + impurities)
Fulgurite
Fulgurite (Lechatelierite)
Black Obsidian
Volcanic Glass (SiO2 + impurities)
Tumbled black stone, likely black obsidian
Obsidian — volcanic glass, primarily SiO₂
Gold Sheen Obsidian
Volcanic Glass (SiO2 + Fe3O4 / Gas Inclusions)
Common Opal (Potch)
Hydrated Silica (SiO2·nH2O)
Limonite and Goethite (Ironstone)
Hydrous Iron Oxide Mixture (FeO(OH)·nH2O)
Obsidian
Volcanic glass
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
Amber-bearing rough specimen
Fossilized plant resin (amber; organic mineraloid), commonly succinite
White Opal (Common)
Hydrated Silica (SiO2·nH2O)
Obsidian
Volcanic Glass (Amorphous SiO2)
Obsidian
Volcanic Glass (SiO2 rich)
Polished mahogany obsidian (probable)
Volcanic glass; chiefly rhyolitic silica-rich glass (SiO₂), compositionally near rhyolite
Obsidian
Volcanic Glass (Amorphous Silicon Dioxide)
Pearl
Calcium Carbonate (Aragonite) with Conchiolin; formula: CaCO3
Pearl (Biogenic Mineraloid)
Calcium carbonate (Aragonite) and Conchiolin, CaCO3
Obsidian
Volcanic Glass (70% or more SiO2)
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
Obsidian
Obsidian (Amorphous volcanic glass, predominantly SiO2)
Obsidian
Volcanic glass
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
Limonite (Iron Ore)
Hydrated Iron(III) Oxide-Hydroxide (FeO(OH)·nH2O)
Pearl (Biogenic Mineraloid)
Calcium carbonate (CaCO3) primarily as Aragonite
Black Obsidian
Obsidian (Volcanic Glass, SiO2 + impurity)
Likely obsidian (possibly tektite or slag glass)
Volcanic glass; primarily SiO₂, noncrystalline
Obsidian
Volcanic Glass (Primary composition: SiO2 - Silicon Dioxide)
Obsidian
Volcanic Glass (SiO2)
Obsidian (black volcanic glass), possibly slag or basalt
Obsidian; chiefly amorphous volcanic silica glass, approximately SiO₂-rich rhyolitic composition
Obsidian
Obsidian (Volcanic Glass, SiO2 + impurities)
Amber with Inclusion
Succiniferous fossil resin (C10H16O)
Black Pearl (Tahitian Pearl)
Aragonite / Calcite (CaCO3) with Conchiolin
Obsidian arrowhead
Volcanic glass; predominantly SiO₂, with minor feldspar, pyroxene, and iron oxides
Mahogany Obsidian
Volcanic Glass with Hematite (SiO2 + Fe2O3)
Black Obsidian
Volcanic Glass (SiO2 + impurities like Fe3O4)
Snowflake Obsidian
Spherulitic Obsidian (Volcanic Glass with Cristobalite inclusions)
Obsidian
Obsidian (Volcanic Glass, SiO2 + impurities)
Snowflake Obsidian
Hydrated Volcanic Glass (primarily SiO2) with Cristobalite inclusions
Obsidian
Volcanic Glass (SiO2)
Black obsidian (likely)
Volcanic glass; primarily silica-rich, noncrystalline SiO₂ composition
Polished black stone, likely black obsidian
Obsidian (volcanic glass), primarily rhyolitic silica glass
Obsidian
Obsidian (volcanic glass), primarily SiO2 (silicon dioxide)