Fired Clay Brick (Anthropic Rock substitute)
Anthropogenic polycrystalline ceramic (predominantly Mullite and Quartz: Al6Si2O13 + SiO2)
metamorphic (man-made / anthropic)
Category
Mineraloid (Anthropogenic)
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Limonite (Ironstone) Concretion
FeO(OH)·nH2O (Hydrous ferric oxide)
sedimentary
Obsidian
Obsidian (Volcanic Glass)
igneous
Snowflake Obsidian
Volcanic Glass with Spherulite inclusions (Chemical composition: 70–75% SiO2 + MgO, Fe3O4)
igneous
Obsidian (Black Obsidian)
Obsidian (Volcanic Glass)
igneous
Obsidian
Volcanic Glass (Amorphous SiO2)
igneous
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
igneous
Common Opal with Host Rock
Opal (Hydrated silica, SiO2·nH2O)
mineral
Mahogany Obsidian
Obsidian (volcanic glass with hematite/magnetite inclusions)
igneous
Precious Opal
Hydrated Silica (SiO2·nH2O)
mineral
Precious Opal
Hydrated Silicon Dioxide (SiO2·nH2O)
gemstone
Black Opal (Triplet)
Hydrated Silica (SiO2·nH2O)
mineral
Obsidian
Volcanic glass (silica-rich rhyolitic melt; primarily SiO₂)
igneous
Obsidian
Obsidian (Extrusive Volcanic Glass)
igneous
Obsidian
Volcanic Glass (comprised primarily of SiO2)
Igneous
Opalite
Synthetic Glass (Hydrated Crystalline Silicon Dioxide simulation)
mineral
Mahogany Obsidian
Volcanic glass (SiO2 + Fe2O3)
igneous
Black Obsidian
Volcanic Glass (predominantly SiO2, Silicon Dioxide)
igneous
Limonite (Yellow Ochre)
Limonite (an amorphous mixture of hydrated iron oxides, primarily FeO(OH)·nH2O)
mineral
Snowflake Obsidian
Volcanic Glass (spherulitic Obsidian) - SiO2 (with Cristobalite inclusions)
igneous
Black Obsidian
Volcanic glass (Amorphous silicates)
igneous
Common Opal (Potch)
Hydrated Silica (SiO2·nH2O)
mineral
Limonite with Quartz (Gossan)
Hydrated iron(III) oxide-hydroxide mixture (FeO(OH)·nH2O) with Silicon Dioxide (SiO2)
Mineral
White Opal (Common)
Hydrated Silica (SiO2·nH2O)
mineral
Obsidian
Volcanic glass (Amorphous silicon dioxide)
igneous
Obsidian
Volcanic glass
igneous
Mahogany Obsidian
Volcanic Glass (SiO2 with Fe/Mg oxides)
igneous
Black Obsidian
Obsidian (Volcanic Glass), primarily SiO2 (Silicon Dioxide)
igneous
Asphalt (Bituminous pavement)
Bituminous concrete / Asphalt
Sedimentary (Anthropogenic)
Concrete Fragment
Hardened Portland cement and mineral aggregate
sedimentary (anthropogenic)
Sea Glass (Frosted Glass)
Amorphous Silica (SiO2) with various additives
Man-made material (Anthropogenic 'mineraloid')
Limonite and Goethite (Ironstone)
Hydrous Iron Oxide Mixture (FeO(OH)·nH2O)
sedimentary
Paper (Cellulose)
Cellulose (C6H10O5)n
Organic (Anthropogenic)
Green Slag Glass
Amorphous Silicon Dioxide (with metallic impurities)
Igneous (Anthropogenic)
Obsidian
Volcanic Glass (Primary composition: SiO2 - Silicon Dioxide)
igneous
Obsidian
Obsidian (principally SiO2 with MgO and Fe3O4)
igneous
Concrete
Anthropogenic Sedimentary Conglomerate (Cement mixture: typically Ca2SiO4, Ca3SiO5, Ca3Al2O6)
sedimentary (artificial)
Obsidian
Volcanic Glass (Amorphous silicon dioxide with trace impurities)
igneous
Tektite (likely Australite)
Tektite (no specific chemical formula as it's a natural glass of variable composition, mostly SiO2, Al2O3, FeO, MgO, CaO, K2O, Na2O, TiO2)
Mineral (specifically a mineraloid)
Limonite (Iron Ore)
Limonite (an FeO(OH)·nH2O mineraloid, not a true mineral due to variable composition)
Mineral
Amber
Succinite (specifically for Baltic amber); C10H16O (Variable organic compound)
mineral
Metal Chain (Likely Steel or a Steel Alloy)
Steel (primarily iron and carbon); specific alloy unknown
Man-made Object (Metal/Alloy)