Mahogany Obsidian
Volcanic Glass with Hematite (SiO2 + Fe2O3)
igneous
Category
Mineraloid (Anthropogenic)
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Black Obsidian
Volcanic Glass (SiO2 + impurities like Fe3O4)
igneous
Opal
Hydrated silica (SiO2 "NH2O)
mineraloid
Snowflake Obsidian
Spherulitic Obsidian (Volcanic Glass with Cristobalite inclusions)
igneous
Obsidian
Obsidian (Volcanic Glass, SiO2 + impurities)
igneous
Snowflake Obsidian
Hydrated Volcanic Glass (primarily SiO2) with Cristobalite inclusions
igneous
Obsidian
Volcanic Glass (SiO2)
igneous
Amber
Amber (C10H16O)
mineral
Opal
Hydrated amorphous silica (SiO2·nH2O)
mineral
Granite Pebble
Granite (Phaneritic intrusive igneous rock comprising Quartz, Feldspar, and Mica)
igneous
Amber with Inclusion
Succiniferous fossil resin (C10H16O)
mineraloid
Black Pearl (Tahitian Pearl)
Aragonite / Calcite (CaCO3) with Conchiolin
mineral
Black obsidian (likely)
Volcanic glass; primarily silica-rich, noncrystalline SiO₂ composition
igneous
Polished black stone, likely black obsidian
Obsidian (volcanic glass), primarily rhyolitic silica glass
igneous
Obsidian
Obsidian (volcanic glass), primarily SiO2 (silicon dioxide)
igneous
Obsidian
Volcanic glass (mainly SiO2 with inclusions)
igneous
Mahogany Obsidian
Volcanic glass containing Hematite or Magnetite (SiO2 + Fe2O3)
igneous
Obsidian
Obsidian (Volcanic Glass)
igneous
Limonite (Iron Stone/Ocher)
Limonite (FeO(OH)·nH2O)
mineral
Obsidian
Amorphous volcanic glass (primarily SiO2)
igneous
Limonite/Goethite on Shale
Hydrous ferric oxides (FeO(OH)·nH2O) often associated with argillaceous rock
sedimentary
Snowflake Obsidian
Spherulitic Volcanic Glass (primarily SiO2 with Cristobalite inclusions)
igneous
Snowflake Obsidian
Volcanic Glass with Cristobalite inclusions (70–75% SiO2)
Igneous
Black Obsidian
Obsidian (Amorphous Silicon Dioxide)
igneous
Snowflake Obsidian
Volcanic Glass with Cristobalite Inclusions
igneous
Precious Opal
SiO2·nH2O (Hydrated Silicon Dioxide)
mineraloid
Chert Arrowhead
Cryptocrystalline microcrystalline Quartz (SiO2)
sedimentary
Quartzite Arrowhead (Archaeological Lithic)
Recrystallized Quartz (SiO2)
metamorphic
Common Opal in Host Rock
Hydrated Silica (SiO2·nH2O)
mineraloid
Common Opal
Hydrated Amorphous Silica (SiO2·nH2O)
mineraloid
Obsidian
Obsidian (Volcanic Glass)
igneous
Mahogany Obsidian
Obsidian (volcanic glass with hematite/magnetite inclusions)
igneous
Black Obsidian
Obsidian (Volcanic Glass, SiO2+)
igneous
Snowflake Obsidian
Spherulitic Volcanic Glass (primarily SiO2)
igneous
Limonite (Yellow Ochre)
Hydrated iron(III) oxide-hydroxide (FeO(OH)·nH2O)
mineral
Black Obsidian
Volcanic Glass (Primary composition: SiO2 - Silicon Dioxide)
igneous
Limonite (Yellow Ochre)
Limonite (Hydrated iron(III) oxide-hydroxide, FeO(OH)·nH2O)
mineral
Limonite/Goethite Concretion
Hydrated Iron(III) Oxide-hydroxide (FeO(OH)·nH2O)
sedimentary
Obsidian
Obsidian (Volcanic Glass)
igneous
Limonite (Ironstone)
Limonite (Hydrated iron(III) oxide-hydroxide, FeO(OH)·nH2O)
mineral
Limonite (Iron Ore)
Limonite (Hydrated iron oxide - FeO(OH)·nH2O)
mineral
Amber (Copal)
Succiniferous Resin
mineraloid