Unidentified dark pebble
Undetermined; possibly polished basalt, chert, or iron-rich stone
mineral
Category
Industrial Byproduct (Often Mistaken For Obsidian Or Mineral)
Browse industrial byproduct (often mistaken for obsidian or mineral) specimens identified by the Rock Identifier community.
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Polished mahogany obsidian
Volcanic glass (mostly SiO₂), commonly called mahogany obsidian
igneous
Snowflake Obsidian
Volcanic Glass with Cristobalite inclusions
igneous
Ironstone concretion
Siderite or Limonite concretion (FeCO3 or FeO(OH)·nH2O)
sedimentary
Mahogany Obsidian
Volcanic Glass with Hematite or Magnetite (SiO2 + Fe2O3)
igneous
Obsidian
Volcanic Glass (Mainly SiO2)
igneous
Mahogany Obsidian
Volcanic Glass with Hematite/Magnetite (SiO2 + Fe2O3)
igneous
Sandstone Concretion
Ferruginous Sandstone Concretion (SiO2 + FeO(OH))
sedimentary
Sodalite
Sodalite (Na8(Al6Si6O24)Cl2)
mineral
Green Aventurine
Quartz with Fuchsite inclusions (SiO2 + K(Al,Cr)2AlSi3O10(OH)2)
mineral
Polished black stone, likely black obsidian
Obsidian (volcanic glass; mainly SiO₂)
igneous
Ironstone Concretion
Siderite or Hematite-rich Concretion (FeCO3 / Fe2O3)
sedimentary
Sandstone Concretion
Sedimentary Concretion (SiO2 or CaCO3 cemented)
sedimentary
Obsidian
Volcanic Glass
igneous
Black Obsidian
Volcanic Glass (Silicon Dioxide with impurities)
igneous
Mudstone/Siltstone with Liesegang Bands
Argillaceous Sedimentary Rock with Chemical Banding
sedimentary
Dendritic Agate (Tumbled)
Silicon Dioxide (SiO2) with inclusions
mineral
Likely black obsidian
Volcanic glass; chiefly rhyolitic silica-rich melt (approximately 70–80% SiO₂)
igneous
Sulfur
Native Sulfur (S)
mineral
Sulfur (with possible Cullet Glass or Slag imitation)
Native Sulfur (S8)
mineral
Sandstone with Dendritic Inclusions
Quartzose Sandstone
sedimentary
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
igneous
Black Obsidian
Amorphous volcanic glass (SiO2)
igneous
Blue Apatite
Fluorapatite / Ca5(PO4)3F
mineral
Sandstone Concretion
Limonitic Sandstone Concretion
sedimentary
Specular Hematite (Specularite) in Matrix
Specularite (Fe2O3)
mineral
Amazonite
KAlSi3O8 (Potassium Aluminum Silicate) - a variety of Microcline Feldspar
mineral
Obsidian
Obsidian (Volcanic Glass)
igneous
Obsidian
Obsidian (Volcanic Glass)
igneous
Chrysocolla in Quartz (Gem Silica)
Cu2-xAlx(H2-xSi2O5)(OH)4·nH2O (Chrysocolla) / SiO2 (Quartz)
mineral
Sandstone Concretion
Clastic sedimentary rock (primarily Silica, SiO2, or Calcium Carbonate, CaCO3)
sedimentary
Jasper (Multi-colored) / Sea Glass Slag
Silicon Dioxide (SiO2) with impurities of Iron Oxide
Sedimentary (if natural Jasper) or Artificial (if Slag)
Green Glass Cullet / Recycled Glass
Amorphous Silicon Dioxide (SiO2) with various metal oxides
Man-made Glass (Not a natural rock or mineral)
Fossilized belemnite guard (likely)
Belemnitella or related belemnite; fossil calcite (CaCO₃)
fossil
Ironstone Concretion (Limonite/Goethite)
Iron-rich sedimentary rock (FeOx)
sedimentary
Blue Dumortierite Quartz
Dumortierite Inclusions in Quartz (SiO2 with Al7(BO3)(SiO4)3O3)
mineral
Black Spinel
Magnesium Aluminum Oxide (MgAl2O4)
mineral
Black Obsidian
Volcanic Glass (SiO2 + MgO / Fe3O4)
igneous
Yellow Jasper with Dendritic Inclusions
Silicon Dioxide (SiO2) with Manganese/Iron Oxide inclusions
sedimentary
Tumbled smoky quartz (probable)
Quartz, silicon dioxide (SiO₂), smoky variety
mineral
Green Rutilated Quartz
Silicon Dioxide with Actinolite inclusions (SiO2 + Ca2(Mg,Fe)5Si8O22(OH)2)
mineral
Quartzite
Quartzite (SiO2)
metamorphic