Petrified Wood
Silicified Wood (SiO2 permineralization)
fossil
Category
Not A Geological Specimen
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Petrified Wood
Silicified Wood (SiO2)
fossil
Petrified Wood
Silicified wood (principally SiO2)
sedimentary
Pyrite in Slate
Iron Sulfide (FeS2) in Slate host matrix
metamorphic
Petrified Wood
Silicified Wood (SiO2)
metamorphic
Ironstone Concretion (Moqui Marble type)
Ironstone Concretion (Fe2O3 with SiO2 core)
sedimentary
Limonite / Goethite (Iron Ore Mineral nodule)
FeO(OH)·nH2O / FeO(OH)
mineral
Stromatolite
Biogenic sedimentary rock (Calcium carbonate / Dolomite)
sedimentary
Basalt with Quartz Vein
Aphanitic Mafic Igneous Rock with Quartz (Silica) Intrusion
igneous
Septarian Nodule or Mud Crack Fossil
Septarian Nodule (Concretion)
sedimentary
Polished Septarian Nodule
Septarian calcite–aragonite concretion, commonly with barite or celestine
sedimentary
Gneiss
Metamorphic Gneiss
metamorphic
Tektite (Indochinite)
Tektite (SiO2 + Al2O3)
mineraloid
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Petrified Wood
Silicified Wood (SiO2)
mineral
Granite
Felsic intrusive igneous rock
igneous
Glauconite sand
Glauconite (K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2
sedimentary
Kambaba Jasper (Crocodile Jasper)
Stromatolite (Fossilized Algae within Microcrystalline Quartz), SiO2
sedimentary
Pyrite Concretion
Iron Sulfide (FeS2) in Sedimentary Matrix
sedimentary
Likely iron-rich concretion or weathered rock pebble
Uncertain from the image; possibly an iron-oxide-cemented concretion (goethite/hematite)
sedimentary
Likely weathered granite or granitic pebble
Granite; primarily quartz (SiO₂), feldspar, and mica
igneous
Rounded dark river pebble (likely basalt or fine-grained andesite)
Probable basalt; plagioclase and pyroxene, with minor olivine or iron oxides possible
igneous
Weathered quartz-bearing rock fragment
Indeterminate; likely quartz-rich granite or silicified host rock with iron-oxide staining
mineral
Granite Pebble with Quartz/Feldspar Vein
Intrusive Felsic Igneous Rock (Granite)
igneous
Weathered iron-rich rock (possibly ironstone)
Likely ferruginous sandstone or ironstone; exact identification requires examination
sedimentary
Rounded gray pebble, likely basalt or fine-grained volcanic rock
Probable basalt; exact identification is uncertain from the photograph
igneous
Flint with Fossil Inclusion
Cryptocrystalline quartz (SiO2) enclosing fossilized organic remains
sedimentary
Biotite granite (possibly granodiorite)
Coarse-grained granitoid composed mainly of quartz (SiO₂), potassium feldspar, plagioclase, biotite, and minor amphibole
igneous
Flint / Chert
Microcrystalline Quartz (SiO2)
sedimentary
Petrified Wood
Silicified Wood (SiO2)
fossil
Ironstone concretion
Iron-oxide-cemented sediment, commonly goethite (FeO(OH)) and/or hematite (Fe₂O₃)
sedimentary
Muscovite Schist
Metamorphic rock primarily composed of quartz and muscovite mica
metamorphic
Ventifact
Wind-abraded rock (Ventifact)
sedimentary
Fossil Coral (Petoskey Stone / Rugose Coral)
Hexagonaria percarinata (or similar fossilized rugose/tabulate coral)
fossil
Quartz-veined Sandstone Pebble
Quartzose Sandstone with Quartz Veinlets
sedimentary
Tektite (Indochinite)
Tektite (High-silica natural glass)
meteorite
Petrified Wood
Silicified Wood (primarily SiO2)
mineral
Sandstone Concretion
Sedimentary Clastic Rock (Silicate-rich)
sedimentary
Amethyst Geode
Silicon Dioxide with trace inclusions of Iron (SiO2)
mineral
Chipped Glass/Plastic Fragment
Silicon dioxide (SiO2) for glass (amorphous) or various polymer compounds for plastic
Man-made material (simulant/artifact)
Gold-bearing Quartz Vein in Mafic Rock
Hydrothermal Quartz Vein within Greenschist/Amphibolite facies (SiO2 with Au)
metamorphic
Basalt pebble
Basalt; fine-grained mafic volcanic rock, chiefly plagioclase and pyroxene with possible olivine
igneous