Tiny amber-colored crystal fragment
Indeterminate; possibly quartz, feldspar, mica, or a sulfide mineral
mineral
Category
Mineral Precipitate (Anthropogenic Context)
Browse mineral precipitate (anthropogenic context) specimens identified by the Rock Identifier community.
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Hag Stone
Perforated Sedimentary Rock (typically Sandstone or Siltstone)
sedimentary
Cobaltian Calcite (Cobaltoan Calcite)
Cobalt-bearing Calcite (Ca,Co)CO3
mineral
Baked-clay ceramic fragment (likely brick or pottery)
Fired clay, primarily aluminosilicate minerals; not a natural rock
sedimentary
Terrazzo (Synthetic Composite Rock)
Cementitious or Epoxy Resin-bound Aggregates
Man-made metamorphic-style composite
Red Sandstone
Arenite (Ferruginous Sandstone)
sedimentary
Mystic Topaz
Aluminum silicate fluoride hydroxide with titanium coating (Al2SiO4(F,OH)2)
mineral
Cupronickel (on a 1981 Mexico 20 Pesos coin)
Copper-Nickel Alloy (Cu75Ni25)
mineral
Sandstone (Nut-stone / Cup-stone artifact)
Quartz Arenite / Worked Sedimentary Rock
sedimentary
Obsidian (likely Apache tear or flaked obsidian)
Volcanic glass; primarily rhyolitic silica glass (SiO₂-rich, non-crystalline)
igneous
Limonite-pseudomorph after Pyrite (Prophecy Stone)
Goethite and Limonite secondary minerals (FeO(OH)·nH2O) replacing Pyrite (FeS2)
mineral
Yellow Jasper
Chalcedony (SiO2) with iron oxide inclusions
mineral
Sea Glass
Amorphous Silica (Anthropogenic glass) - SiO2
mineral
Leopard Skin Jasper
Silicon Dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Concrete Fragment
Artificial Conglomerate (Cement and Aggregate)
sedimentary
Ironstone Concretion (Limonite/Goethite)
Ferruginous Sandstone or Limonite (FeO(OH)·nH2O)
sedimentary
Asphalt (Bituminous Concrete)
Asphaltum / Bitumen-Aggregate Matrix
Technonatural composite (often containing sedimentary/igneous aggregate)
Black Tourmaline (Schorl)
Schorl (Complex sodium iron aluminum borosilicate)
mineral
Ironstone Concretion (Moqui Marble)
Iron-oxide concretion (Fe2O3 / FeO(OH))
sedimentary
Quartz (Iron-stained)
Silicon Dioxide (SiO2)
mineral
Sandstone Concretion
Limonitic Sandstone Concretion
sedimentary
Cullet Glass (Slag Glass)
Amorphous Silicon Dioxide (Industrial byproduct)
mineraloid
Citrine
Citrine (Silicon Dioxide, SiO2)
mineral
Greenschist
Chlorite Schist (Greenschist Facies)
metamorphic
Sodalite
Sodalite (Na8(Al6Si6O24)Cl2)
mineral
Sandstone (likely Fossilized Wood or Concrete Simulacrum)
Arenite / Silicified Wood / Anthropogenic Concrete
sedimentary
Quartzite Arrowhead
Quartzite (SiO2 silicon dioxide)
metamorphic
Slag (Industrial Glassy Byproduct)
Anthropogenic silicate byproduct (Slag)
Mineral-like byproduct (often mistaken for igneous rock or meteorite)
Granite Thin Section
Granitic rock (Phaneritic texture)
igneous
Chalcedony Geode / Agate Nodule
Cryptocrystalline Quartz (SiO2)
mineral
Glass
Amorphous Silicon Dioxide (SiO2)
mineraloid
Titanium Aura Quartz (Bismuth-coated Druzy)
Silicon Dioxide (SiO2) with Titanium/Metal vapor coating
mineral
Granite
Granite (Phaneritic igneous rock)
igneous
Quartz (Iron-stained)
Silicon Dioxide (SiO2)
mineral
Zebra Jasper
Tetragonal Silicon Dioxide (Quartz) with impurities
sedimentary
Greenstone / Greenschist
Greenschist (containing Chlorite, Epidote, Actinolite)
metamorphic
Chert (Arrowhead/Projectile Point)
Microcrystalline Quartz (SiO2)
sedimentary
Chert Arrowhead
Cryptocrystalline Quartz (SiO2)
sedimentary
Seashell (Cone Snail Shell)
Conus sp. (Calcium Carbonate, CaCO3)
fossil
Possible tektite or iron-rich slag-like natural specimen
Uncertain; possibly natural glass (tektite) or magnetite-rich rock
mineral
Ferruginous Sandstone Concretion (Ironstone Phosphorite)
Ferruginous Sandstone (variable Fe-oxide/hydroxide composition)
sedimentary
Possible tektite or volcanic glass specimen
Natural silica glass; composition commonly near SiO₂, but exact identification requires chemical testing
mineral