Obsidian (likely)
Volcanic glass; primarily silica-rich rhyolitic composition (approximately 70–75% SiO₂)
igneous
Category
Man Made Byproduct (Often Mistaken For Obsidian Or Emerald)
Browse man made byproduct (often mistaken for obsidian or emerald) specimens identified by the Rock Identifier community.
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Not a geological specimen
N/A (man-made object)
N/A
Likely chert (flint)
Microcrystalline quartz (SiO₂), likely chert; exact identification is uncertain from the image alone
sedimentary
Dendritic sandstone
Sandstone with Manganese Oxide dendrites
sedimentary
Dendrite (Manganese Oxide Dendrites)
Psilomelane or Pyrolusite on Matrix (typically MnO2)
mineral
Coal (Bituminous Coal)
Caustobiolith / Sedimentary Rock
sedimentary
Quartzite
Metamorphic Quartzite (SiO2)
metamorphic
Milky Quartz with Dendritic Inclusions
Silicon Dioxide (SiO2) with impurities
mineral
Red Quartzite
Quartzite (Metamorphosed Quartz Arenite)
metamorphic
Manganese Dendrite on Siltstone
Manganese Oxide (pyrolusite or psilomelane) Dendrites
mineral/sedimentary
Pyrite (Fool's Gold)
Iron Disulfide (FeS2)
mineral
Green obsidian (likely moldavite)
Natural volcanic glass; if extraterrestrial-impact glass, moldavite (tektite)
gemstone
Amethyst
Silicon Dioxide (SiO2)
mineral
Serpentinized ultramafic rock (serpentinite)
Serpentinite; chiefly serpentine-group minerals, Mg₃Si₂O₅(OH)₄, with possible magnetite, olivine, pyroxene, and brucite
metamorphic
Chert (variations include Flint)
Microcrystalline or cryptocrystalline Quartz (SiO2)
sedimentary
Amethyst
Amethyst (Silicon Dioxide - SiO2 with Iron impurities)
mineral
Obsidian (likely snowflake or volcanic-glass variety)
Volcanic glass, predominantly rhyolitic in composition; mainly SiO₂ with minor Al, Na, K, Fe, and Ca
igneous
Chert (often called Flint in archaeological contexts)
Microcrystalline or cryptocrystalline Silica (SiO2)
sedimentary
Lepidodendron Fossil (Scale Tree)
Lepidodendron sp.
fossil
Quartzite
Metamorphic Quartzite (SiO2)
metamorphic
Sandstone
Clastic Sedimentary Rock
sedimentary
Emerald
Beryl (Be₃Al₂Si₆Oထ₈) with Chromium/Vanadium impurities
gemstone
Quartzite
Metamorphic Quartzite (primarily SiO2)
metamorphic
Iron Slag (Industrial Byproduct)
Anthropogenic pyrometallurgical residue
mineral
Sandstone with Dendritic Inclusions
Quartzose Sandstone
sedimentary
Black Onyx
Silicon Dioxide (SiO2) with parallel banding
mineral
Quartzite
Metamorphic Quartzite (primarily SiO2)
metamorphic
Serpentine
Serpentinite (group of minerals based on (Mg,Fe,Ni,Al,Zn,Mn)2-3(Si,Al,Fe)2O5(OH)4)
metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
metamorphic
Apache Tear (Obsidian)
Obsidian / Amorphous Volcanic Glass (primarily SiO2)
igneous
Yellow Calcite
Calcium Carbonate (CaCO3)
mineral
Dumortierite Quartz
Al7(BO3)(SiO4)3O3
mineral
Dendritic Limestone
Calcite with Manganese Oxide (Manganese Dendrites)
sedimentary
Sandstone
Arenite (SiO2, often with CaCO3 or Fe2O3 cement)
sedimentary
Quartzite
Metamorphic Quartzite
metamorphic
Ferruginous Quartz (Iron-stained Quartz)
Quartz with Iron Oxide inclusions (SiO2 with Fe2O3)
mineral
Rhodonite
Manganese Silicate (Mn,Fe,Mg,Ca)SiO3
mineral
Siltstone/Sandstone (possibly Wonderstone or Picture Sandstone)
Clastic Sedimentary Rock (primarily SiO2 with Iron Oxide inclusions)
Sedimentary
Amethyst
Silicon dioxide (SiO2) with iron impurities
mineral
Siltstone with iron staining
Siltstone (primarily SiO2 with FeO(OH) coatings)
sedimentary
Quartzite Cobble
Quartzite (SiO2)
metamorphic