Olivine (Peridotite)
Magnesium iron silicate ((Mg, Fe)2SiO4)
igneous
Category
Not A Geological Specimen
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Limonite / Iron Oxide Concretion
Hydrated iron(III) oxide-hydroxide, FeO(OH)·nH2O
mineral
Kambaba Jasper
Stromatolite (fossilized algae)
sedimentary
Sandstone with Quartz Crystal Infill
Quartz-cemented quartz arenite
sedimentary
Biotite Schist
Schist (Biotite-dominated)
metamorphic
Graphic Granite
Graphic Granite (Granitic Pegmatite)
igneous
Peanut Wood
Silicified (Petrified) Wood - SiO2 (Silicon Dioxide)
sedimentary
Green Jasper / Metavesuvianite-bearing rock
Silica-rich microcrystalline quartz aggregate / Green Jasper
igneous
Conglomeratic gravel / pebble-rich concrete-like rock
Polymictic conglomerate (likely an unconsolidated gravel surface; exact identification uncertain from the image)
sedimentary
Quartzite (Lithic Artifact)
Quartzite (SiO2)
metamorphic
Chert (Arrowhead/Tool variety)
Microcrystalline Quartz (SiO2)
sedimentary
Amethyst
Quartz (Silicon Dioxide) SiO2 + Fe4
mineral
Fossilized Coral
Cnidaria (Anthozoa), often replaced by Calcium Carbonate (CaCO3) or Silica (SiO2)
sedimentary
Granite Pebble (River Rock)
Granite
igneous
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Septarian Nodule (Micro-fragment)
Septarian Nodule / Concretion (CaCO3 + CaMg(CO3)2 + Quartz)
sedimentary
Petrified Wood
Silicified Wood (primarily SiO2)
sedimentary
Fossil Coral (Petoskey Stone / Rugose Coral)
Hexagonaria percarinata (Order: Rugosa, Fossilized Calcium Carbonate CaCO3)
sedimentary
Petrified Wood
Silicified Wood (primarily SiO2)
sedimentary
Petrified Wood
Silicified Wood (primarily Quartz/Chalcedony, SiO2)
mineral
Fossil coral (likely tabulate or colonial coral)
Fossilized colonial coral; exact genus indeterminate from the photograph
fossil
Quartzite Pebble
Metamorphosed Sandstone (SiO2)
metamorphic
Silver Nuggets (Natural or Cast)
Native Silver (Ag)
mineral
Weathered vesicular volcanic rock, likely basaltic scoria
Vesicular basalt/scoria; chiefly plagioclase, pyroxene, and iron oxides
igneous
Agatized Fossil (Druzy Agate)
Silicon Dioxide (SiO2) replacing organic matter
sedimentary
Weathered granite (granite cobble)
Granite, chiefly quartz, feldspar, and mica; dark vein likely mafic mineral concentration or iron-oxide-stained fracture
igneous
Septarian Nodule
Septarian Concretion (Calcium Carbonate/Aragonite/Calcite)
sedimentary
Fossiliferous Limestone
Calcium Carbonate (CaCO3) with Biogenic Fragments
sedimentary
Petrified Wood
Silicified wood (principally Silicon Dioxide, SiO2)
sedimentary
Gold Ore (in Quartz/Sulfide matrix)
Native Gold (Au) in Quartz (SiO2) and Pyrite (FeS2)
mineral
Moqui Marble (Shaman Stone)
Ironstone Concretion (Goethite/Hematite over Sandstone)
sedimentary
Sandstone Pebble with Mineral Encrustation
Quartz Sandstone with Calcite/Halite Crust
sedimentary
Moqui Marble (Iron Concretion)
Hematite/Goethite Concretion (Fe2O3 / FeO(OH))
sedimentary
Petrified Wood
Silicified wood (Quartz variant, SiO2)
sedimentary
Fulgurite
Lechatelierite (Silica glass tube)
mineral
Portable Ceramic Space Heater
Polished Acrylonitrile Butadiene Styrene (ABS) Plastic with Ceramic Heating Elements
not a rock (synthetic/industrial object)
Porphyritic Basalt or Porphyritic Andesite
Porphyritic Extrusive Igneous Rock
igneous
Banded Siltstone
Banded Siltstone / Laminated Siltstone
sedimentary
Polymict breccia (likely impact breccia)
Polymict lithic breccia; composition appears basaltic/mafic clasts in a dark, fine-grained matrix
igneous
Yellow faceted gemstone, likely citrine or synthetic glass
Citrine (quartz, SiO₂) is the leading natural possibility; visual identification is uncertain from the photograph
gemstone
Vesicular Basalt with Epidote/Amygdaloidal Basalt
Amygdaloidal Basalt (Mg, Fe)2SiO4 + Ca2(Al, Fe)3(SiO4)3(OH)
igneous
Limonite (Ironstone) Concretion
FeO(OH)·nH2O (Hydrous ferric oxide)
sedimentary