Limonite or Ironstone Nodule
FeO(OH)·nH2O (Hydrated iron(III) oxide-hydroxide)
sedimentary
Category
Not A Geological Specimen
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Limonite and Goethite encrusted Chert/Ironstone
Hydrated Iron Oxide (FeO(OH)·nH2O) with cryptocrystalline Silica (SiO2)
sedimentary
Chert (Pink Jasper)
Microcrystalline Quartz (SiO2)
sedimentary
Portable Ceramic Space Heater
Polished Acrylonitrile Butadiene Styrene (ABS) Plastic with Ceramic Heating Elements
not a rock (synthetic/industrial object)
Petrified Wood
Silicified Wood (primarily SiO2)
sedimentary
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Milky Quartz (Gold-bearing Prospecting Specimen)
Silicon Dioxide (SiO2)
mineral
Quartzite with Mafic Intrusion (Gneiss/Schist Contact)
Metamorphic Quartzite (SiO2) with Amphibole/Biotite Schist
metamorphic
Granite Pegmatite with Muscovite Mica
Granite Pegmatite (Silicon Dioxide and complex silicates)
igneous
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Chipped Glass/Plastic Fragment
Silicon dioxide (SiO2) for glass (amorphous) or various polymer compounds for plastic
Man-made material (simulant/artifact)
Artificial Rock Face (Faux Rock)
Glass Fiber Reinforced Concrete (GFRC)
man-made/construction material
Quartz with Orthoclase Feldspar
Silicon Dioxide (SiO2) with Potassium Aluminum Silicate (KAlSi3O8)
mineral
Banded Calcite (often commercially called 'Mexican Onyx')
Calcium Carbonate (CaCO3)
mineral
Quartz Vein in Sandstone
Quartz (SiO2) in Clastic Sedimentary Rock
sedimentary
Chalcedony in Host Rock
Chalcedony (SiO2)
mineral
Dendritic Siltstone
Siltstone with Manganese Dendrites (MnO2)
sedimentary
Heulandite with Stilbite
Heulandite-Ca ((Ca,Na)2-3Al3(Al,Si)2Si13O36·12H2O) and Stilbite-Ca (NaCa4(Si27Al9)O72·28H2O)
mineral
Quartzite
Quartzite (SiO2)
metamorphic
Quartz Geode
Crystalline Silicon Dioxide (SiO2) in a Geode
mineral
Chert (Flint)
Microcrystalline Quartz (SiO2)
sedimentary
Moqui Marble (Shaman Stone)
Ironstone Concretion (Fe2O3 with a sandstone core)
sedimentary
Schorl (Black Tourmaline)
Schorl (Sodium Iron Aluminum Borosilicate Hydroxide), NaFe3Al6(BO3)3Si6O18(OH)4
mineral
Petrified Wood
Silicified Wood (primarily SiO₂ / Silicon Dioxide)
mineral
Orbicular Granite
Orbicular Granidiorite / Plutonic Igneous Rock
igneous
Desert Rose
Gypsum (variety Selenite) or Barite, CaSO4·2H2O
mineral
Gold-bearing Quartz Vein in Mafic Rock
Hydrothermal Quartz Vein within Greenschist/Amphibolite facies (SiO2 with Au)
metamorphic
Banded Iron Formation (BIF)
Banded Iron Formation (SiO2 + Fe2O3)
sedimentary
Native Gold Nugget
Native Gold (Au)
mineral
Garnet-Mica Schist
Garnetiferous Porphyroblastic Schist
metamorphic
Basalt
Basalt (dominated by Plagioclase Feldspar and Pyroxene)
igneous
Honeycomb Coral Fossil
Favosites (extinct genus of tabulate coral)
sedimentary
Quartz Geode
Silicon Dioxide (SiO2) within a secondary sedimentary structure
sedimentary
One Pound Coin (UK)
Nickel-Brass Alloy (Cu-Zn-Ni)
mineral
Chalcedony in Limestone Host Rock
Silicon Dioxide (SiO2) within Calcium Carbonate (CaCO3)
Mineral within Sedimentary Rock
Septarian Nodule
Septarian Concretion (CaCO3, CaMg(CO3)2, SiO2)
sedimentary
Pegmatite with Quartz and Muscovite Mica
Granitic Pegmatite (KAl2(AlSi3O10)(OH)2 + SiO2)
igneous
Septarian Nodule (Septaria)
Septarian Nodule (Calcium Carbonate/Aragonite/Calcite Concretion)
sedimentary
Fossiliferous Limestone
Biomicrite / Limestone with fossils
sedimentary
Sandstone (Ferruginous Concretion)
Ferruginous Sandstone Concretion / SiO2 with Fe2O3 cement
sedimentary
Limonite (Ironstone)
Limonite (Hydrated iron(III) oxide-hydroxide, FeO(OH)·nH2O)
mineral
Metal Chain (Likely Steel or a Steel Alloy)
Steel (primarily iron and carbon); specific alloy unknown
Man-made Object (Metal/Alloy)