Man Made Byproduct (Often Mistaken For Obsidian Or Emerald)

Concrete / Conglomerate (Man-made)

Artificial Conglomerate (Cementitious Composite)

Dyed Crackle Quartz (Green)

Quenching-treated Quartz (Silicon Dioxide, SiO2)

Ring with an Orange Inlay

N/A (Man-made object)

Slag

Anthropogenic Vitrification Product / Silicate Slag

Green Slag Glass

Amorphous Silicon Dioxide (with metallic impurities)

Concrete fragment with Aggregate

Anthropogenic Concrete with Calcarious and Siliceous Aggregate

Glass

Amorphous Silicon Dioxide (SiO2)

Slag (Industrial Byproduct)

Ferro-silicate glass (Slag)

Ferrochrome Slag

Anthropogenic slag (Fe-Cr alloy waste)

Blue glass-like tumbled specimen

Most likely cobalt-blue slag glass or manufactured glass; not confidently identifiable as a natural mineral from the image

Industrial Slag

Anthropogenic Vitreous Slag

Black glassy fragment, likely obsidian or industrial glass

Volcanic glass (obsidian), chiefly amorphous SiO₂; identification uncertain from image

Chert Concretion (with typical hematite/limonite staining)

Sedimentary Concretion (SiO2 with FeO(OH)⋅nH2O)

Tumbled black stone, likely black obsidian

Obsidian (volcanic glass; chiefly silica-rich rhyolitic composition)

Opalite

Synthetic Opalized Glass

Sandstone Concretion

Clastic Sedimentary Rock (primarily SiO2 with mineral cement)

Terracotta (Man-made ceramic brick fragment)

Baked clay / High-iron ceramic (Silicate-based ceramic)

Sandstone Concretion

Clastic sedimentary rock (primarily Quartz SiO2)

Mother of Pearl (Nacre)

Aragonite (CaCO3) with Organic Matrix

Black tumbled stone, possibly obsidian

Obsidian (volcanic glass; predominantly SiO₂), identification uncertain from image

Opalite

Man-made glass (traditionally simulated Opal)

Boxwork or Septarian Concretion

Septarian nodule / Boxwork weathering

Green obsidian (likely molded or heat-treated glass-like specimen)

Volcanic glass; predominantly rhyolitic composition (silica-rich amorphous SiO₂)

Cobalt Glass Slug (Cullet)

Man-made Silicate Glass with Cobalt Oxide (CoO)

Opalite

Man-made Synthetic Glass (Silicon Dioxide with metal additives)

Aqua Aura Quartz

Silicon Dioxide (SiO2) bonded with Gold (Au)

Aventurine

Silicon dioxide (Quartz) with inclusions (KAl2(AlSi3O10)(OH)2)

Goldstone (Brown/Gold)

Aventurine Glass (Man-made glass with Copper inclusions)

Blue slag glass / industrial smelter slag

Man-made iron-rich silicate slag; composition variable, commonly Fe–Ca–Mg–Al silicates with glassy phases

Opalite

Synthetic Opalised Glass

Opalite

Synthetic Silicon Dioxide (SiO2)

Polished black pebble, likely basalt

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

Green glassy slag (often sold as “sea glass” or “green obsidian”)

Industrial vitreous slag; primarily amorphous silicate glass, composition variable

Green Slag Glass

Amorphous Silica Glass (Anthropogenic)

Dioptase

Dioptase (CuSiO2(OH)2)

Polished obsidian

Volcanic glass; predominantly rhyolitic SiO₂

Cobalt Glass Slug (Man-made Glass)

Amorphous Silica with Cobalt Oxide (SiO2 + CoO)

Slag Glass (Leland Blue variant)

Anthropogenic Vitreous Silicate

Carborundum (Silicon Carbide)

Silicon Carbide (SiC)

Blue Glass or Slag Glass

Amorphous Silica (Anthropogenic Glass)

Green sea glass (likely slag glass or bottle glass)

Man-made soda-lime silicate glass; not a naturally occurring mineral

Dioptase

Dioptase (CuSiO3 · H2O)