Not A Geological Specimen

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Yellow faceted gemstone, likely citrine or synthetic glass

Citrine (quartz, SiO₂) is the leading natural possibility; visual identification is uncertain from the photograph

Petrified Wood

Silicified Wood (primarily SiO2)

Pyrite in Shale

Iron Sulfide (FeS2) in Argillaceous Shale

Limonite (Ironstone) Concretion

FeO(OH)·nH2O (Hydrous ferric oxide)

Red Jasper

Silicon Dioxide (Microcrystalline Quartz, SiO2)

Sandstone Concretion

Siliciclastic Concretion

Mica Schist / Granite

Mica Schist (Silicate metamorphic rock)

Coral Fossil (Petoskey-style or Colonial)

Hexagonaria percarinata (Order: Rugosa)

Basalt with Chert or Jasper Inclusion

Igneous basalt / sedimentary chert nodule

Septarian nodule fragment

Calcite-filled septarian concretion, commonly with a mudstone or limestone matrix

Pale green mica-rich rock (possibly chlorite schist)

Likely chlorite schist; identification is uncertain from the photograph

Polished amethyst bead fragments

Amethyst, purple quartz (SiO₂)

Petrified Wood

Silicified Wood / Chalcedony (SiO2)

Fossiliferous Limestone with Rugose Coral

Calcite (CaCO3) containing a Rugosa (Horn Coral) fossil

Artificial Rock Face (Faux Rock)

Glass Fiber Reinforced Concrete (GFRC)

Ring with an Orange Inlay

N/A (Man-made object)

Fossilized Coral (Petoskey Stone or similar Rugose Coral)

Hexagonaria percarinata (or similar Rugose/Tabulate coral)

Fossilized Coral (Petoskey-like or Favosites)

Anthozoa (Fossilized Coral)

Gneiss Pebble

Gneiss (Metamorphic Foliated Rock)

Stromatolite (stromatolitic limestone)

Laminated microbial carbonate, chiefly calcite (CaCO₃); precise species or age cannot be determined from the photo

Iron-rich metamorphic rock, likely banded iron formation fragment

Banded iron formation (BIF), chiefly hematite–magnetite with chert; exact identification requires testing

Weathered iron-rich sandstone or ironstone

Ferruginous sandstone, likely limonite/goethite-cemented quartz arenite

Chert / Flint (Arrowhead)

Microcrystalline quartz (SiO2)

Graphic Granite

Graphic Granite (Pegmatitic Alkali Feldspar and Quartz)

Banded Agate (Agatized Geode Slice)

Silicon Dioxide (SiO₂)

Weathered iron-stained rock fragment

Uncertain from the image; likely an iron-oxide-stained, quartz- and feldspar-bearing rock

Quartz Geode / Druzy Quartz

Silicon Dioxide (SiO2)

Amygdaloidal Basalt

Amygdaloidal Basalt (containing quartz/agate or zeolite fill)

Banded Sedimentary Rock (Siltstone/Mudstone with concretion)

Siltstone with Ferruginous Banding

Granite

Phaneritic Felsic Igneous Rock

Rough quartz-rich rock, possibly granite or pegmatite

Likely quartz and feldspar with possible mica; exact rock type cannot be determined from the image

Eclogite with Garnet

Eclogite (Omphacite-Garnet Metamorphic Rock)

Vesicular basalt (lava rock)

Basalt, a mafic volcanic rock composed mainly of plagioclase feldspar and pyroxene, commonly with olivine

Quartz Geode (Nodule)

Silicon Dioxide (SiO2)

Basalt cobble in concrete aggregate

Basalt; chiefly plagioclase feldspar and pyroxene, with possible olivine and iron-titanium oxides

Basalt

Mafic extrusive igneous rock

Pink granite fragment

Granite, chiefly quartz, feldspar, and mica

Gold Ore

Auriferous Quartz and Sulfide Mineralization in Host Rock

Greenstone (likely chlorite- or actinolite-rich metabasalt)

Metamorphosed mafic volcanic rock; commonly greenschist-facies basalt, composed chiefly of chlorite, actinolite, epidote, and albite

Weathered limestone or concrete-like calcareous rock

Limestone; predominantly calcite (CaCO₃), possibly containing dolomite and silicate impurities

Likely bituminous coal

Coal, predominantly carbon-rich organic matter with variable maceral and mineral content