Obsidian
Obsidian (Volcanic Glass)
igneous
Category
Amorphous Solid
Browse amorphous solid specimens identified by the Rock Identifier community.
Black Obsidian
Volcanic Glass (SiO2 + impurities)
Igneous
Anthracite Coal
Anthracite (Highly Metamorphosed Coal)
sedimentary
Bumblebee Jasper
Fossiliferous Volcanic Rock (composed of Calcium Carbonate, Manganese Oxides, and Arsenic Sulfides)
igneous
Iron Slag
Anthropogenic Vitreous Silicate (Byproduct of Smelting)
Mineral-like byproduct
Limonite (Iron Stone/Ocher)
Limonite (FeO(OH)·nH2O)
mineral
Coquina
Biogenic Limestone (Calcite, CaCO3)
sedimentary
Yellow Ochre / Limonite
Limonite (Hydrated Iron(III) Oxide-Hydroxide, FeO(OH)·nH2O)
mineral
Artificial Rock Face (Faux Rock)
Glass Fiber Reinforced Concrete (GFRC)
man-made/construction material
Mahogany Obsidian
Volcanic Glass with Hematite inclusions (SiO2 + Fe2O3)
igneous
Amber
Succinite (formula varies, primarily C10H16O)
Mineraloid (Organic)
Opalite
Man-made Synthetic Glass (Silicon Dioxide with metal additives)
mineral
Spiny Oyster Shell
Spondylus varians (Biogenic Calcium Carbonate)
mineral
Amber
Succinite
Organic mineraloid
Limonite (Iron Stone/Gossen)
Limonite (FeO(OH)·nH2O)
mineral
Chrysocolla
Chrysocolla; (Cu,Al)2H2Si2O5(OH)4·nH2O
mineral
Limonite (Iron Ore)
FeO(OH)·nH2O (Hydrated iron(III) oxide-hydroxide mixture)
mineral
Limonite (Ochreous)
FeO(OH)·nH2O (Hydrated Iron Oxide)
mineral
Tiffany Stone
Fluoritized Opal Beryllium Tuff (composed of Fluorite; CaF2, Opalized SiO2, Bertrandite, Chalcedony, and Quartz)
metamorphic
Goldstone
Aventurine glass (Synthetic glass with copper inclusions)
mineraloid / man-made glass
Limonite (Iron Ore/Bog Iron)
Hydrated Iron(III) Oxide-Hydroxide (FeO(OH)·nH2O)
mineral
Precious Opal
Hydrated Silica (SiO2·nH2O)
mineraloid
Opalite (Synthetic Moonstone/Sea Opal)
Silicon Dioxide (SiO2) glass with metallic inclusions
Synthetic/Man-made Glass
Obsidian Arrowhead
Volcanic Glass (Primary composition: SiO2)
igneous
Baltic Amber (Butterscotch or Egg Yolk Variety)
Succinite (C10H16O)
Organic Gemstone (fossilized resin)
Anthracite Coal
Anthracite (Carbon based fossil fuel)
metamorphic
Limonite (Hydrated Iron Oxide / Bog Iron)
FeO(OH)·nH2O
Mineral (Sedimentary context)
Sandstone Concretion
Moqui Marble / Iron-oxide Concretion (SiO2 with Hematite/Goethite)
sedimentary
Snowflake Obsidian
Vitreous Volcanic Rock (Amorphous Silicate), SiO2
igneous
Obsidian
Volcanic Glass (Amorphous Silicon Dioxide, SiO2)
igneous
Common Green Opal
Hydrated amorphous silicon dioxide (SiO2·nH2O)
mineral
Common Opal
Hydrated amorphous form of silica (SiO2·nH2O)
mineral
Obsidian (Apache Tear)
Volcanic Glass (Amorphous Silicon Dioxide, SiO2)
igneous
Slag Glass (Cullet)
Amorphous Silica (man-made), primarily SiO2 with trace metal oxides
Mineraloid / Synthetic Glass
Amber
Fossilized Tree Resin (Amorphous Hydrocarbon)
Mineral
Black Opal
Amorphous Hydrated Silica (SiO2·nH2O)
mineral
Opal
Hydrated Amorphous Silica (SiO2·nH2O)
Mineral
Pink Opal
Hydrated Amorphous Silica (SiO2·nH2O)
mineraloid
Cullet Glass (Man-made Glass Slag)
Amorphous Silica (SiO2) with chemical additives
Mineraloid
Red Slag Glass
Amorphous Silica (Industrial byproduct with metallic oxide dopants)
Mineraloid / Industrial Byproduct
Obsidian
Volcanic Glass (Amorphous Silicon Dioxide)
igneous
Opal
Hydrated Amorphous Silica (SiO2·nH2O)
Mineral