Obsidian
Obsidian (Volcanic Glass, SiO2 + impurity)
Category
Browse mineral like byproduct (technogenic) specimens identified by the Rock Identifier community.
Obsidian
Obsidian (Volcanic Glass, SiO2 + impurity)
Obsidian
Volcanic glass (high silica volcanic rock)
Serpentinite
Serpentinite (composed primarily of Serpentine group minerals, Mg3Si2O5(OH)4)
Prehnite
Prehnite (Ca2Al(AlSi3O10)(OH)2)
Chalcedony (Common Opal or Agate variant)
Silicon Dioxide (SiO₂)
Dendritic Agate (Tree Agate)
Chalcedony (Silicon Dioxide, SiO2) with Manganese or Iron Oxide inclusions
Petrified Wood
Silicified wood (primarily SiO2)
Gneiss
Gneiss (High-grade Regional Metamorphic Rock)
Fluorite
Calcium Fluoride (CaF2)
Schist with Quartz/Mica
Mica Schist (primarily Muscovite and Quartz)
Shale
Laminated Mudstone
Celadonite in Basalt (Green Earth)
Celadonite (K(Mg,Fe2+)(Fe3+,Al)Si4O10(OH)2)
Prehnite
Prehnite (Ca2Al(AlSi3O10)(OH)2)
Quartz (Clear Quartz/Rock Crystal)
Silicon Dioxide (SiO2)
Tufa (Vesicular Limestone)
Tufa (form of Calcium Carbonate, CaCO3)
Obsidian
Volcanic Glass (70-75% SiO2)
Druzy Quartz Geode (Oco or Moroccan variety)
Silicon Dioxide (SiO2)
Septarian Nodule (Dragon Stone)
Septarian Geode (CaCO3 + Mg + Fe)
Sandstone
Arenite (SiO2 primarily)
Quartz Geode
Silicon Dioxide (SiO2)
Muscovite (White Mica)
Muscovite - Potassium aluminum silicate: KAl2(AlSi3O10)(F,OH)2
Quartz (Milky or Cloudy Quartz)
Silicon Dioxide (SiO2)
Quartz (Iron-stained)
Silicon Dioxide (SiO2)
Sandstone (Picture Sandstone)
Arenite (primarily SiO2 with iron oxide impurities)
Sandstone (likely Arkosic)
Clastic Sedimentary Rock
Sandstone (likely Arkosic or Quartzose)
Sandstone (SiO2 dominated)
Limonite Concretion (Ironstone)
Limonite / Goethite (FeO(OH)·nH2O)
Clear Quartz (Rock Crystal)
Silicon Dioxide (SiO2)
Petrified Wood
Silicified Wood (SiO2)
Ruby, Emerald, and Sapphire (Corundum and Beryl)
Corundum (Al2O3) and Beryl (Be3Al2Si6O18)
Muscovite Mica (with Quartz)
Muscovite (KAl2(AlSi3O10)(OH)2)
Red Garnet (likely Almandine or Pyrope)
Garnet group: X3Y2(SiO4)3 (e.g., Almandine: Fe3Al2Si3O12)
Biotite (Black Mica)
Biotite [K(Mg,Fe)3(AlSi3O10)(F,OH)2]
Sandstone (with banding)
Arenite (primarily SiO2)
Banded Onyx (Mexican Onyx / Travertine)
Calcite (CaCO3) - Banded Travertine
Obsidian
Obsidian (principally SiO2 + MgO, Fe3O4)
Fluorite Octahedron
Fluorite (Calcium Fluoride, CaF2)
Agate Geode Node
Cryptocrystalline Quartz (SiO2)
Halite
Sodium Chloride (NaCl)
Quartz / Common Opal Transition
Silicon Dioxide (SiO2)
Fossil Coral (Favosites Honeycomb)
Favosites (Genus), Phylum Cnidaria, Class Anthozoa
Sandstone (Ferruginous)
Arenite (primarily SiO2 with Fe2O3 staining)