Not A Geological Specimen

Likely moonstone ring

Moonstone, a feldspar variety with adularescence; typically orthoclase (KAlSi₃O₈), sometimes with albite intergrowths

Basalt fragments in a light-colored host rock

Basalt (mafic volcanic rock; chiefly plagioclase, pyroxene, and sometimes olivine)

Quartz with Orthoclase Feldspar

Silicon Dioxide (SiO2) with Potassium Aluminum Silicate (KAlSi3O8)

Ironstone (iron-rich sandstone or concretion)

Ferruginous sandstone, cemented by iron oxides/hydroxides such as hematite (Fe₂O₃) and goethite (FeO(OH))

Quartz Cobble (River Pebble)

Quartz (Silicon Dioxide - SiO2)

Dendritic Siltstone

Siltstone with Manganese Dendrites (MnO2)

Quartz Vein in Sandstone

Quartz (SiO2) in Clastic Sedimentary Rock

Banded gneiss (likely amphibolite-rich gneiss)

Banded gneiss; composition commonly quartz, feldspar, mica and/or amphibole

Ironstone Nodule

Ironstone (Ferruginous Rock)

Heulandite with Stilbite

Heulandite-Ca ((Ca,Na)2-3Al3(Al,Si)2Si13O36·12H2O) and Stilbite-Ca (NaCa4(Si27Al9)O72·28H2O)

Speckled rounded stone, possibly basalt or diorite

Indeterminate mafic/intermediate igneous rock; likely fine-grained basaltic or dioritic material

Graphitic schist

Graphite-rich pelitic schist; primarily quartz, mica, and graphite

Decorative polished stone tile, likely white marble or limestone

Calcite-rich marble (CaCO₃), possibly veined limestone; exact identification requires testing

Conglomerate (possibly breccia)

Polymictic clastic conglomerate; rounded clasts in a dark, likely volcanic-lithic matrix

Quartz vein in foliated metamorphic rock

Likely quartz-bearing schist or gneiss; visible crystal is quartz (SiO₂)

Dark gray rounded cobble, likely basalt or fine-grained metamorphic rock

Likely basalt (plagioclase–pyroxene rock); exact identification requires testing

Quartz Geode

Crystalline Silicon Dioxide (SiO2) in a Geode

Pumice

Pumice; highly vesicular volcanic glass, typically rhyolitic to dacitic in composition

Fluorescent glassy mineral specimen, possibly hyalite opal

Hyalite (hydrated amorphous silica, SiO₂·nH₂O), tentative

Rounded granite or granitic gneiss cobble

Granite, chiefly quartz, potassium feldspar, plagioclase, and biotite/hornblende

Garnet Schist

Almandine-bearing Mica Schist

Granite Pebble

Granite (Plutonic Igneous Rock)

Moqui Marble (Shaman Stone)

Ironstone Concretion (Fe2O3 with a sandstone core)

Schorl (Black Tourmaline)

Schorl (Sodium Iron Aluminum Borosilicate Hydroxide), NaFe3Al6(BO3)3Si6O18(OH)4

Weathered limestone

Calcite-rich limestone (primarily CaCO₃)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Weathered metamorphic boulder, likely schist or gneiss

Quartz–feldspar–mica metamorphic rock; exact identification requires a fresh surface

Weathered volcanic rock, likely vesicular basalt or scoria

Basaltic volcanic rock; predominantly plagioclase, pyroxene, and possibly olivine with iron-oxide weathering

Petrified Wood

Silicified Wood (primarily SiO₂ / Silicon Dioxide)

Likely granite

Granite; a coarse-grained rock composed mainly of quartz, feldspar, and mica or other dark minerals

Weathered mafic igneous rock, likely basalt

Basalt (fine-grained mafic volcanic rock; exact identification is uncertain from the image)

Orbicular Granite

Orbicular Granidiorite / Plutonic Igneous Rock

Desert Rose

Gypsum (variety Selenite) or Barite, CaSO4·2H2O

Likely garnet-bearing rock fragment

Garnet-bearing schist or gneiss; garnet is commonly almandine, Fe₃Al₂(SiO₄)₃

Granite pebble

Granite, typically quartz–feldspar–mica aggregate

Mica-rich granite (likely biotite granite)

Biotite granite; mainly quartz (SiO₂), alkali/feldspar, and biotite mica

Banded Iron Formation (BIF)

Banded Iron Formation (predominantly Hematite and Chert)

Garnet-Mica Schist

Garnetiferous Porphyroblastic Schist

Gold ring with a dark, possibly gemstone setting

Gold alloy; the dark setting is not identifiable from the image

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Banded gneiss pebble

Foliated gneiss, typically quartz–feldspar–mica bearing

Green mica schist (probable)

Mica-rich schist, likely dominated by muscovite or chlorite with quartz