Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
Category
Browse mineral (or mineraloid if microcrystalline) specimens identified by the Rock Identifier community.
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
Likely obsidian (possibly tektite or slag glass)
Volcanic glass; primarily SiO₂, noncrystalline
Black Obsidian
Obsidian (Volcanic Glass, SiO2 + impurity)
Limonite (Iron Ore)
Limonite (an amorphous mixture of hydrated iron oxides, primarily FeO(OH)·nH2O)
Obsidian
Volcanic Glass (Primary composition: SiO2 - Silicon Dioxide)
Jet
Lignite (Anthracite-grade compact coal)
Limonite (Ironstone)
Limonite (mixture of hydrated iron(III) oxide-hydroxides)
Conch Pearl
Calcareous concretion (CaCO3)
Opal
Hydrated Silica (SiO2·nH2O)
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)
Amber
Amber (C10H16O)
Snowflake Obsidian
Volcanic Glass with Cristobalite Inclusions
Pearl
Calcium carbonate (CaCO3) - mainly Aragonite with Conchiolin
Limonite (Iron Ore)
Limonite (FeO(OH)·nH2O)
Limonite (Iron Ore)
Hydrated Iron(III) Oxide-Hydroxide (FeO(OH)·nH2O)
Pearl
Aragonite / Calcium Carbonate (CaCO3)
Mahogany Obsidian
Volcanic glass containing Hematite or Magnetite (SiO2 + Fe2O3)
Obsidian
Obsidian (Volcanic Glass)
Obsidian
Amorphous volcanic glass (primarily SiO2)
Limonite/Goethite on Shale
Hydrous ferric oxides (FeO(OH)·nH2O) often associated with argillaceous rock
Black Obsidian
Obsidian (Amorphous Silicon Dioxide)
Pearl
Aragonite and Conchiolin (CaCO3 + organic protein)
Opal
Hydrated Amorphous Silica (SiO2·nH2O)
Limonite (Yellow Ochre)
Limonite (Hydrated iron(III) oxide-hydroxide, FeO(OH)·nH2O)
Common Opal
Hydrated Amorphous Silica (SiO2·nH2O)
Limonite (Yellow Ochre)
Hydrated iron(III) oxide-hydroxide (FeO(OH)·nH2O)
Limonite (Ironstone)
Limonite (Hydrated iron(III) oxide-hydroxide, FeO(OH)·nH2O)
Limonite (Iron Ore)
Limonite (Hydrated iron oxide - FeO(OH)·nH2O)
Mahogany Obsidian
Obsidian (volcanic glass with hematite/magnetite inclusions)
Black Obsidian
Obsidian (Volcanic Glass, SiO2+)
Snowflake Obsidian
Spherulitic Volcanic Glass (primarily SiO2)
Black Obsidian
Volcanic Glass (Primary composition: SiO2 - Silicon Dioxide)
Obsidian
Obsidian (Volcanic Glass)
Amber with Organic Inclusions
Succinite (fossilized resin)
Limonite (Iron Ore)
Limonite (Hydrous ferric oxides), generic formula FeO(OH)·nH2O
Obsidian
Volcanic Glass (SiO2)
Amber
Succinates
Opal
Hydrated Silica (SiO2·nH2O)