Ironstone Concretion / Limonite Node
Limonite (Hydrated Iron Oxide, FeO(OH)·nH2O) with Goethite/Hematite
sedimentary
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.
Apache Tear
Obsidian (Hydrated Volcanic Glass) - SiO2 (with impurities)
igneous
Apache Tear
Obsidian (Hydrated Silica / Amorphous Volcanic Glass)
igneous
Quartzite
Quartzite (primarily composed of SiO O₂)
Sedimentary Rock
Diamond (or Cubic Zirconia simulant)
Carbon (C) - Diamond / Zirconium dioxide (ZrO2) - CZ
mineral
Snowflake Obsidian
Volcanic Glass (SiO2 + impurities)
igneous
Snowflake Obsidian
Hydrated Volcanic Glass (primarily SiO2) with Cristobalite inclusions
igneous
Snowflake Obsidian
Spherulitic Obsidian (primarily SiO2)
igneous
Black Obsidian with white veins
Volcanic Glass (70–75% SiO2)
igneous
Quartzite
Quartzite (SiO2)
metamorphic
Ferruginous Quartzite (Red Chert/Jasper-like)
Metamorphosed Quartzite with Hematite inclusions (SiO2 + Fe2O3)
metamorphic
Ferruginous Sandstone (Ironstone Nodules)
Ferruginous Quartz-Arenite (with Goethite/Hematite cement)
sedimentary
Dalmatian Stone
Dalmatian Jasper (actually a Peralkaline Igneous Rock)
igneous
Pink Quartzite
Quartzite (primarily SiO2)
metamorphic
Ferruginous Quartzite (Chert)
Quartzite with Iron inclusions (SiO2 + Fe2O3)
metamorphic
Bryozoan Fossil
Phylum Bryozoa (commonly known as 'moss animals')
sedimentary
Chinese Writing Stone
Porphyritic Basalt (or Andesite) with Feldspar inclusions
igneous
Obsidian and Phantom Quartz
Volcanic Glass (SiO2 + MgO + Fe3O4) and Crystalline Quartz (SiO2)
igneous and mineral
Calcite
Calcium Carbonate (CaCO3)
mineral
Banded Slate (Lithified Mudstone)
Low-grade Metamorphosed Mudstone / Slate
metamorphic
Obsidian
Obsidian (principally SiO2)
igneous
Black Obsidian
Volcanic Glass (SiO2)
igneous
Chert (Nodule)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Ironstone Concretion (Ironstone Gourd)
Limonite/Goethite Concretion (FeOO(H))
sedimentary
Snowflake Obsidian
Spherulitic Obsidian (primarily SiO2 with Cristobalite inclusions)
igneous
Black Spinel
Magnesium Aluminum Oxide (MgAl2O4)
mineral
Snowflake Obsidian
Obsidian with Cristobalite inclusions (Amorphous SiO2 + SiO2 inclusions)
igneous
Quartzite
Quartzite (primarily SiO2)
metamorphic
Chert (Iron-Stained)
Microcrystalline or cryptocrystalline Quartz (SiO2)
sedimentary
Sodalite
Sodalite, Na8(Al6Si6O24)Cl2
mineral
Mahogany Obsidian
Volcanic Glass (Silicate: SiO2 + Fe2O3)
igneous
Mahogany Obsidian
Volcanic Glass with Hematite inclusions (SiO2)
igneous
Opalite
Man-made Glass (SiO2 + additives)
mineraloid (synthetic)
Quartzite
Quartzite (primarily SiO2)
metamorphic
Pyrite in Matrix (Commonly called Fool's Gold)
Iron Sulfide (FeS2)
mineral
Obsidian
Obsidian (Volcanic Glass, primarily SiO2)
igneous
Siltstone
Siltstone (primarily SiO2 with Al2O3)
sedimentary
Ferruginous Sandstone with Ironstone Concretion
Goethite-rich Sandstone (FeO(OH))
sedimentary
Diorite
Diorite
igneous
Mahogany Obsidian
Volcanic Glass (SiO2 + Fe2O3)
igneous
River Rocks (Black)
Various lithologies (e.g., basalt, chert, obsidian for black varieties), mechanically rounded clasts
Sedimentary
Pyrite (Fool's Gold)
Iron Disulfide (FeS2)
mineral