Industrial Byproduct (Often Mistaken For Obsidian Or Mineral)

Tiffany Stone

Bertrandite Fluorite (CaF2 + Be4Si2O7(OH)2)

Sandstone Concretion

Sedimentary Concretion (SiO2 or CaCO3 cemented)

Dendritic Agate (Tumbled)

Silicon Dioxide (SiO2) with inclusions

Obsidian

Volcanic Glass (SiO2)

Snowflake Obsidian

Volcanic glass with Cristobalite inclusions (mostly SiO2)

Obsidian

Obsidian (Volcanic Glass, SiO2 dominated)

Green Rutilated Quartz

Silicon Dioxide with Actinolite inclusions (SiO2 + Ca2(Mg,Fe)5Si8O22(OH)2)

Mahogany Obsidian

Volcanic glass (SiO2 + Fe2O3)

Ironstone (likely Limonite or Goethite nodule)

Hydrothermally altered Ferric Hydroxide (FeO(OH)·nH2O)

Chrysocolla in Quartz (Gem Silica)

Cu2-xAlx(H2-xSi2O5)(OH)4·nH2O (Chrysocolla) / SiO2 (Quartz)

Concretion (Sandstone)

Carbonate-cemented Sandstone Concretion

Apatite

Apatite Group (e.g., Fluorapatite Ca5(PO4)3F, Chlorapatite Ca5(PO4)3Cl, Hydroxylapatite Ca5(PO4)3(OH))

Obsidian

Obsidian (Volcanic Glass)

Sandstone Concretion

Clastic sedimentary rock (primarily Silica, SiO2, or Calcium Carbonate, CaCO3)

Snowflake Obsidian

Volcanic Glass with Cristobalite inclusions

Obsidian

Volcanic Glass (SiO2)

Specular Hematite (Specularite) in Matrix

Specularite (Fe2O3)

Obsidian

Volcanic Glass (SiO2 + minor impurities)

Red Jasper

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Variscite in Matrix

Variscite (AlPO4 · 2H2O)

Mahogany Obsidian

Obsidian (Volcanic Glass) with Hematite or Magnetite inclusions, SiO2 (Silicon Dioxide)

Yellow Aventurine

Quartz containing Muscovite or Mica inclusions (SiO2)

Obsidian

Obsidian (Volcanic Glass), primarily SiO2 (Silicon Dioxide)

Sandstone (with Concretion)

Arenite / Quartzose Sandstone

Obsidian

Volcanic glass (SiO2 - Silicon dioxide predominant composition)

Mahogany Obsidian

Volcanic Glass with Hematite/Magnetite inclusions (SiO2)

Obsidian

Obsidian (principally SiO2 - Silicon Dioxide)

Obsidian

Obsidian (Volcanic Glass, SiO2)

Obsidian

Extrusive igneous volcanic glass (rich in SiO2)

Sandstone Concretion

Septarian or Carbonate-cemented Sandstone Concretion

Obsidian

Volcanic Glass (SiO2 rich)

Quartzite River Rock with Dendrites

Metamorphosed Quartz-rich Sandstone with Manganese Oxide (MnO2) inclusions

Scoria with Calcite Infills

Vesicular Basalt with secondary Calcification (CaCO3)

Obsidian

Volcanic Glass (SiO2 - Silicon Dioxide with impurities)

Boxwork Siderite or Sepatarian Nodule Weathering

Siderite (FeCO3) with secondary mineralization or Boxwork Geode fragment

Pyrite in Quartzite/Graphite Matrix

Iron Sulfide (FeS2)

Sandstone Concretion

Clastic Sedimentary Concretion (primarily SiO2 with Fe2O3 cement)

Snowflake Obsidian

Volcanic glass with Cristobalite inclusions (70–75% SiO2)

Banded Sandstone

Arenite (with iron oxide banding)

Arfvedsonite in Quartz

Arfvedsonite [Na3(Fe2+4Fe3+)Si8O22(OH)2] often hosted in Quartz or Feldspar

Obsidian

Obsidian (Volcanic Glass), primarily SiO2 (Silicon Dioxide)

Mahogany Obsidian

Volcanic glass containing Hematite or Magnetite (SiO2 + Fe2O3)