Weathered iron-rich sandstone or ferruginous siltstone
Clastic sedimentary rock, likely quartz-rich sandstone cemented by iron oxides (Fe₂O₃/Fe₃O₄)
sedimentary
Category
Not A Natural Rock
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Turquoise
Turquoise - CuAl6(PO4)4(OH)8·4H2O
mineral
Banded Chert / Flint
Silicon dioxide (SiO2)
sedimentary
Diamond (in jewelry)
Cubic Carbon (C)
mineral
Granite
Phaneritic high-silica plutonic rock (composed primarily of Quartz, Feldspar, and Mica)
igneous
Yellow Quartz (Citrine-colored Quartz Pebble)
Silicon Dioxide (SiO2)
mineral
Picture Jasper
SiO2
Sedimentary/Mineral
Actinolite (likely fibrous amphibole)
Actinolite, Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂; possibly an actinolite–tremolite specimen
mineral
Ametrine
Quartz (Silicon Dioxide, SiO2)
gemstone
Concrete with Exposed Aggregate
Anthropogenic conglomerate (Concrete)
man-made rock (sedimentary analogue)
Agate (specifically, multi-colored or pastel-dyed agate)
Silicon dioxide (SiO2) - specifically, a cryptocrystalline variety of quartz known as Chalcedony, with banding classified as Agate. (If it were Fluorite, the chemical formula would be Calcium Fluoride - CaF2).
Mineral
Dyed blue quartz or druzy geode (likely)
Quartz, silicon dioxide (SiO₂), probably artificially colored
mineral
Pyrite (Pseudomorph)
Iron Sulfide (FeS2)
mineral
Diamond ring
Diamond (crystalline carbon, C)
gemstone
Aluminum Slag
Anthropogenic Aluminum (Al)
mineral
Opalite
Synthetic Glass (SiO2 + impurities)
mineral
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)
Goldstone (Brown)
Aventurine glass
mineraloid (man-made)
Banded Gneiss (River Rock/Pebble)
Gneiss (specifically a banded variety, likely a orthogneiss or paragneiss depending on parent rock)
Metamorphic Rock
Mammoth Molar Fossil
Mammuthus primigenius (Tooth fragment)
fossil
Synthetic Marbled Aggregate (Footwear Component)
Ethylene-vinyl acetate (Croslite™)
not a rock (man-made polymer)
Milky quartz
Quartz (silicon dioxide, SiO₂)
mineral
Citrine Quartz
Silicon Dioxide (SiO2) with iron impurities
mineral
Ironstone (Limonite/Hematite concretion)
Ferruginous Siltstone / Goethite (FeO(OH))
sedimentary
Quartz heart (likely milky/included quartz)
Quartz, silicon dioxide (SiO₂)
mineral
Tangerine Quartz
Silicon Dioxide (SiO2) with Hematite/Limonite coatings
mineral
Tektite
Natural impact glass
meteorite
Tektite
Natural Impact Glass
meteorite
Tektite (Indochinite)
Impactite (Natural Glass)
meteorite
Diamond jewelry
Diamond (crystalline carbon, C)
gemstone
Likely fossilized shell or carbonate concretion
Indeterminate biogenic calcium carbonate, commonly calcite (CaCO₃)
fossil
Obsidian
Obsidian (principally SiO2 - Silicon Dioxide)
igneous
Scoria (Red Lava Rock)
Scoria (Vesicular Basalt/Andesite)
igneous
Cubic Zirconia (Jewelry Setting)
Cubic Zirconia (ZrO2)
gemstone
Chalcedony (Agate Pebble)
Silicon Dioxide (SiO2)
mineral
Greenschist / Greenstone
Greenschist facies metabasite
metamorphic
Citrine (Heat-treated)
Silicon Dioxide (SiO2)
mineral
Rainbow Hematite (Man-made/Treated)
Tumbled Hematite with Titanium/Anodized coating (Iron(III) oxide, Fe2O3)
mineral
Blue opalite (often sold as synthetic opal)
Opalite glass; amorphous hydrated silica if natural opal (SiO₂·nH₂O)
gemstone
Opalite
Synthetic Glass (Silica-based)
gemstone
Composite Turquoise or Reconstituted Turquoise with Copper inclusions
CuAl6(PO4)4(OH)8·4H2O (Turquoise) mixed with matrix and copper/bronze flakes
mineral
Dyed Quartz (often sold as 'Blue Quartz' or 'Blue Agate')
Silicon Dioxide (SiO2) with artificial pigment
mineral