Not A Geological Specimen

Cullet Glass (Slag Glass)

Amorphous Silicon Dioxide (Industrial Byproduct)

Acrylic or Resin (Synthetic Imitation)

Polymethyl Methacrylate (PMMA) or Polyepoxide

Unidentified dark gray rock fragment

Likely fine-grained basalt or andesite; exact identification requires testing

Porous fossiliferous limestone

Calcitic limestone, predominantly calcium carbonate (CaCO₃), possibly bioclastic or weathered reef limestone

Biotite schist (probable mica schist)

Mica schist; chiefly quartz, biotite mica, and feldspar

Banded iron formation fragment

BIF; hematite–magnetite–chert/quartz assemblage

Foliated metamorphic rock, likely mica schist

Muscovite- or biotite-bearing schist, commonly quartz–feldspar schist

Mica Schist

Schist (muscovite-biotite rich)

Vesicular basalt

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

Weathered iron-rich rock fragment

Indeterminate; likely limonite/goethite-bearing sandstone or laterite

Chert Nodule

Microcrystalline Quartz (SiO2)

Weathered iron-rich rock fragment

Likely limonite/goethite-rich ironstone; exact identification requires testing

Mica Schist (with Muscovite)

Muscovite Mica Schist (KAl2(AlSi3O10)(F,OH)2)

Quartz pebble in concrete

Quartz (SiO₂), embedded in Portland-cement concrete

Sandstone Moqui Marble (Concretion)

Iron oxide concretion (Hematite/Goethite and Quartz)

Ferruginous Sandstone

Arenite with Iron-Oxide cement (primarily Fe2O3 • nH2O)

Bronze or iron-age decorated pottery sherd

Archaeological ceramic fragment; likely fired clay with impressed or molded decoration, not a natural rock

Uncertain fine-grained rock or mineral-bearing specimen

Indeterminate; possible quartz- or feldspar-bearing matrix with reflective grains

Fordite

Anthropogenic paint-rock

Biotite-bearing metamorphic rock, likely schist

Mica schist; chiefly quartz, feldspar, and biotite mica

Sandstone Pebble (River Rock)

Sandstone (Quartz-rich sedimentary rock with iron oxide staining)

Weathered iron-rich rock, possibly limonite-bearing sandstone or laterite

Limonite/goethite-rich ferruginous rock; exact identification requires testing

Biotite-rich granite or granodiorite fragment

Coarse-grained felsic intrusive rock; mainly quartz (SiO₂), feldspar, and biotite mica

Flint (or Chert)

Microcrystalline quartz (SiO2)

Weathered iron-rich rock, possibly limonite-bearing sandstone or laterite

Goethite–hematite (FeO(OH)–Fe₂O₃) in a silicate-rich matrix; exact identification requires testing

Worked flint/chert artifact

Microcrystalline quartz (chalcedony), SiO₂; likely a knapped flint or chert flake/core fragment

Iron-rich sandstone or weathered ironstone

Ferruginous sandstone; primarily quartz (SiO₂) cemented or stained by iron oxides, chiefly hematite (Fe₂O₃) and goethite (FeO(OH))

Druzy Quartz on Chert/Siltstone

Silicon Dioxide (SiO2) on Microcrystalline Silica/Siltstone matrix

Native metal specimen, likely galena or metallic slag

Probably galena (lead sulfide, PbS); identification is uncertain from the image alone

Green glass-like cabochon, likely synthetic glass or resin

Unidentified green transparent material; possibly molded glass, synthetic spinel, or resin

Mixed mineral and rock collection

Predominantly quartz varieties, including amethyst, plus likely calcite, feldspar, mica, and miscellaneous polished stones

Gossan (Iron Hat) with Quartz and Chlorite

Limonite/Goethite-rich Gossan (FeO(OH)·nH2O) with inclusions of Quartz and Chlorite

Polished black stone carving, likely soapstone/steatite

Steatite (massive talc), Mg₃Si₄O₁₀(OH)₂; exact material cannot be confirmed from the image

Pyrite-bearing dark igneous rock, possibly basalt

Likely basalt or mafic volcanic rock with disseminated pyrite (FeS₂); identification is provisional from the photograph

Granite or granitic gneiss

Quartz–feldspar–mica rock; likely granitoid, possibly weakly gneissic

Banded iron formation fragment

Banded iron formation (BIF), composed mainly of hematite/magnetite and chert (SiO₂)

Unidentified dark reddish-brown rock or mineral specimen

Indeterminate from the blurred image; possibly iron-stained quartz, jasper, or a metallic sulfide-bearing rock

Basalt in a vesicular volcanic host rock

Basalt, likely with secondary zeolite or calcite infill

Ironstone Concretion (Limonite/Hematite Nodules)

Ironstone (principally Limonite FeO(OH)·nH2O or Hematite Fe2O3 mixed with silica/clay)

Small metallic mineral fragment

Unidentified metallic sulfide or native-metal fragment

Likely iron-rich sandstone or weathered hematite-bearing rock

Quartz-rich sandstone, possibly ferruginous sandstone (SiO₂ with iron oxides such as hematite/goethite)

Kaibab Limestone

Calcitic limestone, predominantly calcium carbonate (CaCO₃)