Obsidian
Volcanic Glass (70% or more SiO2)
igneous
Category
Man Made Byproduct (Non Geological)
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Quartzite (Orthoquartzite)
SiO2 (Silicon Dioxide) with Iron Oxide inclusions
metamorphic
Obsidian
Obsidian (Volcanic Glass, SiO2 + impurities)
igneous
N/A (Non-Geological Object)
N/A
Obsidian
Volcanic Glass (Rich in SiO2)
igneous
Milky quartz (rough quartz specimen)
Quartz, silicon dioxide (SiO₂)
mineral
Black Obsidian
Obsidian (Amorphous volcanic glass, SiO2)
igneous
Obsidian
Obsidian (Volcanic Glass)
igneous
Painted Sandstone
Sandstone (clastic sedimentary rock) with acrylic/artistic coating
sedimentary
Obsidian
Volcanic Glass (predominantly SiO2)
igneous
Lapis Lazuli
Lapis Lazuli (a rock, not a single mineral; primary mineral is Lazurite (Na,Ca)8(AlSiO4)6(S,SO4,Cl)1-2
Metamorphic rock
Snowflake Obsidian
Obsidian (volcanic glass) with Cristobalite inclusions
igneous
Siltstone
Siltstone (composed of microscopic quartz and clay minerals)
sedimentary
Quartzite
Metamorphic Quartzite (SiO2)
metamorphic
Quartzite
Quartzite (primarily SiO2)
metamorphic
Common Opal (Potch)
Opal (Hydrated silica, SiO2·nH2O)
mineral
Obsidian
Volcanic Glass (Amorphous Silicon Dioxide , SiO2)
igneous
Obsidian
Volcanic Glass (SiO2 + impurities)
igneous
Quartzite
Quartzite (primarily SiO2)
metamorphic
Sandstone with Liesegang Rings
Liesegang-banded Sandstone
sedimentary
Quartzite
Quartzite (primarily SiO2)
metamorphic
Fossilized Oyster Shell
Ostreidae (Calcium Carbonate - CaCO3)
fossil
Quartzite
Quartzite (primarily SiO2)
metamorphic
Sandstone
Clastic sedimentary rock (Quartz arenite/Arkose)
sedimentary
Amber
Resinite / Fossilized Tree Resin
mineral
Sandstone (Pebble)
Sandstone (arenite, arkose, wacke depending on composition)
sedimentary
Gold Ore in Matrix
Native Gold (Au) in Quartz/Limonite host rock
mineral
Banded Calcite or Travertine
Calcium Carbonate (CaCO3)
Sedimentary
Pyrite
Iron Sulfide (FeS2)
mineral
Red cabochon gemstone, likely carnelian or dyed chalcedony
Chalcedony (microcrystalline quartz), SiO₂; exact identification requires testing
gemstone
Quartzite
Quartzite (primarily SiO2)
metamorphic
Quartzite
Quartzite (SiO2)
metamorphic
Obsidian
Amorphous volcanic glass (primarily SiO2)
igneous
Quartzite
Metamorphic Quartzite
metamorphic
Obsidian
Volcanic Glass (Amorphous silicon dioxide with trace impurities)
igneous
Quartzite
Quartzite (primarily SiO2)
metamorphic
Obsidian
Obsidian (Volcanic Glass)
igneous
Crushed Limestone
Calcium Carbonate (CaCO3)
Sedimentary
Snowflake Obsidian
Volcanic glass (SiO2) with Cristobalite (SiO2) inclusions
igneous
Black Obsidian
Volcanic Glass (SiO2 + impurities)
igneous
Polished serpentine pendulum
Serpentine-group minerals, chiefly antigorite/lizardite; approximate formula Mg₃Si₂O₅(OH)₄
metamorphic
Obsidian
Volcanic Glass (SiO2 dominant)
igneous