Industrial Byproduct (Often Mistaken For Obsidian Or Mineral)

Black tourmaline (schorl)

Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

Black Onyx

Silicon Dioxide (SiO2) with parallel banding

Siltstone

Siltstone (SiO2, Fe2O3, Al2O3 mix)

Black polished stone, likely basalt

Basalt; fine-grained mafic volcanic rock composed mainly of plagioclase feldspar, pyroxene, and commonly olivine

Sodalite and Calcite

Na8(Al6Si6O24)Cl2 (Sodalite) and CaCO3 (Calcite)

Polished black stone, likely obsidian

Volcanic glass; chiefly amorphous SiO₂

Sandstone with Liesegang Rings

Quartzose Sandstone with Iron Oxide Precipitation

Polished black stone, likely black obsidian

Obsidian, volcanic glass; primarily silica-rich SiO₂ with minor feldspar, iron, and magnesium

Pyrite

Iron Disulfide (FeS2)

Sandstone Concretion

Carbonate-cemented Sandstone Concretion

Ironstone Concretion (Pot Stone)

Siderite or Limonite Concretion (FeCO3 or FeO(OH)·nH2O)

Sandstone (Wonderstone)

Clastic Sedimentary Rock (primarily SiO2)

Dumortierite Quartz

Dumortierite (Al7BCuO15)

Obsidian

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

Concretion

Calcareous/Siliceous Concretion

Polished red jasper or mahogany obsidian (likely jasper)

Microcrystalline quartz, SiO₂, with iron-oxide inclusions

Smoky Quartz

Quartz (SiO₂)

Polished mahogany obsidian

Volcanic glass, primarily rhyolitic composition (SiO₂-rich); mahogany coloration from iron-oxide inclusions

Variscite in Matrix (often traded as Wardite or Cryptocrystalline Variscite)

Variscite (AlPO4·2H2O)

Polished black stone, likely shungite

Shungite; carbon-rich mineraloid composed mainly of amorphous carbon, with silica and other minerals

Ironstone Concretion

Ironstone (Siderite/Limonite/Goethite)

Ironstone Concretion

Ferruginous Concretion (Fe2O3·nH2O)

Tumbled mahogany obsidian

Volcanic glass; primarily SiO₂ with iron-oxide-rich brown inclusions

Sodalite

Sodalite, Na8(Al6Si6O24)Cl2

Asphalt (Aggregate)

Bituminous macadam / Concrete Aggregate

Siltstone

Siltstone (Detrital Sedimentary Rock)

Diorite (Salt and Pepper Rock)

Diorite

Snowflake Obsidian

Volcanic glass with Cristobalite inclusions (mostly SiO2)

Scoria with Calcite Infills

Vesicular Basalt with secondary Calcification (CaCO3)

Boxwork Siderite or Sepatarian Nodule Weathering

Siderite (FeCO3) with secondary mineralization or Boxwork Geode fragment

Apatite

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

Black obsidian (likely)

Volcanic glass; primarily silica-rich, noncrystalline SiO₂ composition

Polished black stone, likely black obsidian

Obsidian (volcanic glass), primarily rhyolitic silica glass

Obsidian

Volcanic glass (high silica SiO2)

Obsidian

Obsidian (Volcanic Glass)

Sulfur

Native Sulfur (S)

Pyrite with Iron Oxides (Fool's Gold in Matrix)

Iron Sulfide (FeS2)

Quartz (Iron-stained)

Silicon Dioxide (SiO2)

Yellow Aventurine

Silicon Dioxide with inclusions (SiO2)

Quartz (Iron-stained or Milky)

Silicon Dioxide (SiO2)

Green Aventurine

SiO2 (Silicon Dioxide with Fuchsite inclusions)

Quartz Geode

Silicon Dioxide (SiO2)