Chert (Arrowhead)
Microcrystalline Quartz (SiO2)
sedimentary
Category
Mineraloid (Anthropogenic)
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Chert Arrowhead (Lithic Artifact)
Microcrystalline Quartz (SiO2)
sedimentary
Chert Arrowhead (Projectile Point)
Microcrystalline Quartz (SiO2)
sedimentary
Chert Arrowhead
Microcrystalline Quartz (SiO2)
sedimentary
Chert (Arrowhead/Tool variety)
Microcrystalline Quartz (SiO2)
sedimentary
Limonite or Ironstone Nodule
FeO(OH)·nH2O (Hydrated iron(III) oxide-hydroxide)
sedimentary
Black Obsidian
Volcanic Glass (predominantly SiO2)
igneous
Chert Arrowhead (Lithic Tool)
Microcrystalline quartz (SiO2) - Archeological lithic artifact
sedimentary
Chert (specifically Flint Arrowhead)
Silicon dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Likely weathered metallic mineral or slag fragment
Uncertain; possibly limonite/goethite-coated iron mineral, or industrial iron slag
mineral
Basalt
Basalt (Mafic volcanic rock)
igneous
Chert (Arrowhead Fragment)
Microcrystalline Quartz (SiO2)
sedimentary
Black Obsidian
Volcanic Glass (Amorphous SiO2 with trace impurities)
igneous
Chert Arrowhead (Projectile Point)
Microcrystalline Quartz (Chert or Flint)
sedimentary
Chert (Arrowhead/Projectile Point)
Chert (Cryptocrystalline Quartz, SiO2)
sedimentary
Chert (Arrowhead/Projectile Point)
Cryptocrystalline Quartz (SiO2)
sedimentary
Obsidian Arrowhead
Obsidian (Volcanic Glass)
igneous
Asphalt (Bituminous Concrete)
Asphaltum / Bitumen-Aggregate Matrix
Technonatural composite (often containing sedimentary/igneous aggregate)
Slag
Anthropogenic Vitreous Silicate / Ferro-silicate Slag
igneous
Concrete
Anthropogenic Sedimentary Rock (Hydrated Calcium Silicate)
sedimentary (anthropogenic / man-made)
Painted River Pebble (likely Basalt or Greywacke)
Aphanitic Lithic Clast with Anthropogenic Pigment coating
Sedimentary or Igneous
Obsidian
Volcanic Glass (Amorphous silicon dioxide with impurities)
igneous
Black Obsidian
Volcanic glass
igneous
Obsidian
Volcanic Glass
igneous
Obsidian
Volcanic Glass (SiO2 + impurities)
igneous
Fulgurite
Fulgurite (Lechatelierite)
metamorphic
Black Obsidian
Volcanic Glass (SiO2 + impurities)
Igneous
Painted River Rock
Artificially Coated Sedimentary Rock
sedimentary
Titanium Aura Quartz (Bismuth-coated Druzy)
Silicon Dioxide (SiO2) with Titanium/Metal vapor coating
mineral
Tumbled black stone, likely black obsidian
Obsidian — volcanic glass, primarily SiO₂
igneous
Gold Sheen Obsidian
Volcanic Glass (SiO2 + Fe3O4 / Gas Inclusions)
igneous
Ferrochrome Slag
Anthropogenic slag (Fe-Cr alloy waste)
industrial byproduct
Slag (Industrial Glass)
Anthropogenic Vitreous Slag (Post-industrial byproduct)
igneous
Possible tektite or iron-rich slag-like natural specimen
Uncertain; possibly natural glass (tektite) or magnetite-rich rock
mineral
Obsidian
Volcanic glass
igneous
Limonite (Ironstone)
Limonite (mixture of hydrated iron oxides, primarily Goethite α-FeO(OH))
mineral
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
igneous
White Opal
Hydrated Silica (SiO2·nH2O)
mineral
Chert (Arrowhead Debitage or Flake)
Microcrystalline silica (SiO2)
sedimentary
Possible tektite or volcanic glass specimen
Natural silica glass; composition commonly near SiO₂, but exact identification requires chemical testing
mineral
Abalone Shell (Nacre)
Aragonite (CaCO3) - Biogenic Mineral
mineral
Chert (Arrowhead variety)
Chert (SiO2)
sedimentary