Ironstone Concretion (Limonite/Goethite)
Goethite/Limonite concretion (FeO(OH)·nH2O)
Category
Browse industrial byproduct (often mistaken for obsidian or mineral) specimens identified by the Rock Identifier community.
Ironstone Concretion (Limonite/Goethite)
Goethite/Limonite concretion (FeO(OH)·nH2O)
Dendrite (Manganese Oxide Dendrites)
Psilomelane or Pyrolusite on Matrix (typically MnO2)
Milky Quartz with Dendritic Inclusions
Silicon Dioxide (SiO2) with Manganese/Iron oxide inclusions
Dumortierite Quartz
Al7BO3(SiO4)3O3 (inclusion in SiO2)
Sandstone Concretion
Sedimentary Clastic Rock (Silicate-rich)
Quartz (Iron-Stained)
Silicon Dioxide (SiO2)
Chalcopyrite
Copper Iron Sulfide (CuFeS2)
Sodalite
Sodalite [Na8(Al6Si6O24)Cl2]
Concretion
Calcareous or ferruginous concretion
Obsidian (black volcanic glass), possibly with brecciated or weathered fragments
Obsidian; predominantly rhyolitic volcanic glass, typically rich in SiO₂
Chrysocolla
Chrysocolla (Cu2–xAlx(H2–xSi2O5)(OH)4·nH2O)
Blue Apatite
Fluorapatite (Ca5(PO4)3F)
Black tourmaline
Schorl tourmaline, NaFe3Al6(BO3)3Si6O18(OH)4
Ironstone Concretion
Ironstone (Siderite/Goethite/Hematite matrix)
Obsidian
Extrusive igneous volcanic glass (rich in SiO2)
Dumortierite in Quartz
Dumortierite (Al6O3(BO3)(SiO4)3) with Quartz (SiO2)
Metallic iron meteorite fragments (probable)
Iron meteorite, chiefly kamacite (α-(Fe,Ni)) with possible taenite
Black tourmaline (schorl)
Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
Black tourmaline (likely schorl)
Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
Sandstone Concretion
Clastic Sedimentary Concretion (SiO2 with Iron Oxide)
Pyrite
Iron Sulfide (FeS2)
Concretion
Septarian Concretion (Fragmentary)
Banded Sedimentary Rock (Siltstone/Mudstone with concretion)
Siltstone with Ferruginous Banding
Felted Quartz / Chlorite Quartz
Chlorite included Quartz (SiO2 + (Mg,Fe)3(Si,Al)2O5(OH)4)
Obsidian-like volcanic glass (likely slag or natural obsidian)
Obsidian, primarily amorphous volcanic silica glass (approximately SiO₂); identification is uncertain from an image
Black Spinel
Magnesium Aluminum Oxide (MgAl2O4)
Dalmation Stone (Dalmation Jasper)
Peralkaline rock (primarily Feldspar and Quartz with Arfvedsonite spots)
Sandstone (Micaceous Sandstone)
Arenite (SiO2 with KAl2(AlSi3O10)(OH)2 inclusions)
Quartzite with inclusions
Quartzite (SiO2)
Ferruginous Siltstone or Mudstone
Ferruginous Siltstone / Goethitic Sandstone
Polished silver sheen obsidian heart
Obsidian (volcanic glass), primarily rhyolitic silica-rich glass
Obsidian
Volcanic glass (SiO2 + impurities)
Obsidian
Extrusive igneous volcanic glass
Blue Dumortierite Quartz
Dumortierite in Quartz (AlAl6BSi3O18)
Sodalite
Na8(Al6Si6O24)Cl2
Quartz (Iron-stained)
Silicon Dioxide (SiO2)
Obsidian (likely Golden Sheen Obsidian or Rainbow Obsidian, given the subtle sheen visible on some beads)
Obsidian (volcanic glass, predominantly SiO2 with various impurities)
Limonite Concretion
Limonite (Hydrated Iron Oxide) FeO(OH)·nH2O
Limonite Concretion (Ironstone)
Limonite (FeO(OH)·nH2O) / Goethite
Sandstone (likely River-tumbled Picture Sandstone)
Arenite (predominantly SiO2 with iron oxide impurities)
Limestone Concretion (Botryoidal/Calcareous Nodules)
Calcium Carbonate Concretion (CaCO3)
Aventurine
Silicon Dioxide (SiO2) with inclusions