Obsidian Arrowhead
Volcanic Glass (Primary composition: SiO2)
Category
Browse mineraloid (anthropogenic) specimens identified by the Rock Identifier community.
Obsidian Arrowhead
Volcanic Glass (Primary composition: SiO2)
Obsidian
Volcanic Glass (Silica / SiO2)
Mahogany Obsidian
Volcanic glass (Silicon Dioxide with Hematite/Magnetite inclusions)
Obsidian
Obsidian (Volcanic Glass)
Snowflake Obsidian
Spherulitic Volcanic Glass (SiO2 + impurities)
Limonite Concretion
Hydrated iron(III) oxide-hydroxide (FeO(OH)·nH2O)
Obsidian
Volcanic Glass (predominantly SiO2)
Bumblebee Jasper
Calcite with Arsenic and Sulfur inclusions
Obsidian
Obsidian (Volcanic Glass)
Obsidian (Gold Sheen)
Obsidian (SiO2 + impurities)
Mahogany Obsidian
Volcanic Glass (SiO2 + Fe2O3)
Mahogany Obsidian
Volcanic glass containing Hematite or Magnetite (SiO2 + Fe2O3)
Snowflake Obsidian
Volcanic Glass (SiO2) with Cristobalite inclusions
Obsidian
Volcanic Glass (SiO2 + impurities)
Pearl (Biogenic Mineral)
Calcium Carbonate (primarily Aragonite) with Conchiolin; CaCO3
Slag (Anthropogenic Glass/Iron byproduct)
Ferro-silicate Slag
Mahogany Obsidian
Volcanic Glass (predominantly SiO2 with Fe2O3 inclusions)
Green Opal (Prase Opal)
SiO2 · nH2O (Hydrated Silicon Dioxide)
Grooved Maun Ball (Maul/Hammerstone-like Concretion)
Calcareous/Ferruginous Concretion in Sandstone Matrix
Yellow Ocher (Limonite)
Limonite (Hydrated Iron Oxide) - FeO(OH)·nH2O
Limonite (Iron Ore/Sandstone mixture)
Limonite (FeO(OH)·nH2O) often mixed with Goethite and sedimentary matrix
Precious Coral (Red Coral)
Corallium rubrum (Calcium Carbonate, CaCO3)
Obsidian
Volcanic Glass (Amorphous Silica)
Tumbled black stone, likely black obsidian
Obsidian — natural volcanic glass, primarily SiO₂
Obsidian
Obsidian (Volcanic Glass), primarily SiO2 (Silicon Dioxide)
Mahogany Obsidian
Volcanic glass containing Magnetite/Hematite
Obsidian
Volcanic Glass (SiO2)
Obsidian
Volcanic Glass (predominantly SiO2, approximately 70% or more)
Snowflake Obsidian
Obsidian with Spherulitic Cristobalite (SiO2)
Mahogany Obsidian
Obsidian (SiO2 + Fe2O3)
Limonite (Iron Ore)
Hydrous ferric oxides (FeO(OH)·nH2O)
Opal
Hydrated Amorphous Silica (SiO2·nH2O)
Obsidian
Obsidian (Volcanic Glass)
Obsidian
Volcanic Glass (Amorphous Silicon Dioxide)
Obsidian
Volcanic glass
Obsidian
Volcanic Glass (felsic composition)
Mahogany Obsidian
Volcanic Glass with Hematite/Magnetite (SiO2 + Fe2O3)
Obsidian
Volcanic Glass (Silicon Dioxide with impurities)
Obsidian
Obsidian (Amorphous volcanic glass, SiO2 with impurities)
Snowflake Obsidian
Volcanic glass containing Spherulites (SiO2)
Amber
Succinite (with a generalized formula of C10H16O)
Opalite
Man-made Glass (Synthetic Opalized Glass)