Obsidian
Volcanic glass
Category
Browse sedimentary (or mineraloid) specimens identified by the Rock Identifier community.
Obsidian
Volcanic glass
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
Pearl
Organic Mineraloid (CaCO3 + Conchiolin)
Polished mahogany obsidian (probable)
Volcanic glass; chiefly rhyolitic silica-rich glass (SiO₂), compositionally near rhyolite
Obsidian
Volcanic Glass (Amorphous Silicon Dioxide)
Obsidian
Volcanic Glass (Amorphous SiO2)
Obsidian
Volcanic Glass (SiO2 rich)
White Opal (Common)
Hydrated Silica (SiO2·nH2O)
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)
Likely obsidian (possibly tektite or slag glass)
Volcanic glass; primarily SiO₂, noncrystalline
Black Obsidian
Obsidian (Volcanic Glass, SiO2 + impurity)
Obsidian
Volcanic Glass (Primary composition: SiO2 - Silicon Dioxide)
Obsidian
Volcanic Glass (SiO2)
Pearl
Calcium Carbonate (Aragonite) with Conchiolin; formula: CaCO3
Obsidian
Obsidian (Volcanic Glass, SiO2 + impurities)
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)
Red Sandstone
Clastic Sedimentary Mineraloid (predominantly Quartz grains with Iron Oxide cement)
Amber with Inclusion
Succiniferous fossil resin (C10H16O)
Black Pearl (Tahitian Pearl)
Aragonite / Calcite (CaCO3) with Conchiolin
Obsidian
Obsidian (volcanic glass), primarily SiO2 (silicon dioxide)
Obsidian
Volcanic glass (mainly SiO2 with inclusions)
Mahogany Obsidian
Volcanic glass containing Hematite or Magnetite (SiO2 + Fe2O3)
Obsidian
Obsidian (Volcanic Glass)
Snowflake Obsidian
Spherulitic Volcanic Glass (primarily SiO2 with Cristobalite inclusions)
Obsidian
Amorphous volcanic glass (primarily SiO2)
Snowflake Obsidian
Volcanic Glass with Cristobalite inclusions (70–75% SiO2)
Black Obsidian
Obsidian (Amorphous Silicon Dioxide)
Snowflake Obsidian
Volcanic Glass with Cristobalite Inclusions
Obsidian
Obsidian (Volcanic Glass)
Mahogany Obsidian
Obsidian (volcanic glass with hematite/magnetite inclusions)
Black Obsidian
Obsidian (Volcanic Glass, SiO2+)
Snowflake Obsidian
Spherulitic Volcanic Glass (primarily SiO2)