Industrial Byproduct (Anthropogenic Rock)

Possible iron meteorite

Iron meteorite, likely an ataxite or coarse octahedrite; composition mainly Fe–Ni alloy

Clear quartz chips

Quartz (silicon dioxide, SiO₂)

Quartz Vein in Host Rock

Hydrothermal Quartz (SiO2) in Slates/Schists

Rough limestone or dolostone outcrop

Carbonate rock, mainly calcite (CaCO₃) and/or dolomite [CaMg(CO₃)₂]

Garnet-bearing schist

Mica schist with garnet porphyroblasts; garnet likely almandine, Fe₃Al₂(SiO₄)₃

Bauxite

Bauxite (Al(OH)3, AlO(OH), AlOOH)

Basalt

Basalt (Mafic volcanic rock)

Pegmatite

Pegmatite (coarse-grained intrusive igneous rock)

Vesicular Rhyolite

Extrusive igneous rock (high-silica rhyolite)

Pumice

Pumice (SiO2)

Granodiorite / Granite

Granodiorite (containing Quartz SiO2, Plagioclase Feldspar, and Biotite)

Quartzite River Rock

Quartzite (SiO2)

Unidentified brown mineral/rock fragment

Indeterminate from image; possibly iron-stained quartz, feldspar, or weathered limonite

Sandstone

Arenite

Agate

Silicon Dioxide (Chalcedony), SiO2

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Small dark pebble, possibly basalt or iron-rich stone

Undetermined; image alone cannot confirm composition

Garnet in Schist

Almandine Garnet in Mica-Schist (Fe3Al2(SiO4)3)

Quartz with Hematite

Silicon Dioxide (SiO2) with Ferric Oxide (Fe2O3)

Quartz Vein in Host Rock

Silicon Dioxide (SiO2) in matrix

Weathered quartz-rich rock fragment

Indeterminate; likely quartz-bearing silicate rock

Milky quartz

Quartz, silicon dioxide (SiO₂)

Tumbled milky quartz (possibly iron-stained)

Quartz, silicon dioxide (SiO₂)

Vesicular volcanic rock, likely scoria

Scoria (vesicular basaltic to andesitic volcanic rock)

Black Tourmaline (Tumbled)

Schorl (NaFe2+3Al6(Si6O18)(BO3)3(OH)4)

Iron-stained quartz vein rock

Quartz (SiO₂) with iron-oxide/hydroxide staining, likely limonite/goethite

Man-made Metal Pin (Non-geological)

Antimony-Lead Alloy or Zinc/Brass Base with Electroplating

Pumice

Vesicular Felsic Extrusive Igneous Rock

United States Quarter Dollar

Cupronickel Clad Alloy (75% Copper, 25% Nickel over a 100% Copper core)

Ironstone (Limonitic Concretion)

Limonite (FeO(OH)·nH2O) with Goethite and Hematite inclusions

Quartz Geode

Silicon Dioxide (SiO2)

Colorless faceted gemstone, likely quartz

Quartz (SiO₂), tentatively identified from the image

Quartz vein in dark metamorphic rock

Likely quartz-rich vein cutting a biotite- or amphibole-rich metamorphic host; exact host rock cannot be confirmed from the image

Basalt with Vesicles

Vesicular Basalt (Mafic Extrusive)

Pumice

Pumice (a vesicular volcanic glass)

Pumice

Pumice (Amorphous volcanic glass)

Sandstone (Pebble)

Sandstone (SiO2 dominated clastic sedimentary rock)

Garnet Schist

Almandine-mica schist

Amethyst (likely synthetic or treated)

Purple quartz, SiO₂; color caused mainly by trace iron and irradiation

Likely metallic meteorite fragment

Undetermined iron or stony-iron meteorite; mineralogy requires testing

Dyed Blue Agate

Silicon Dioxide (SiO2)

Pumice

Pumice (Vesicular Volcanic Glass)