Man Made Material, Not A Natural Rock Or Mineral Specimen

Chert (Chocolate or Brown Flint)

Chert (SiO2)

Small quartz-rich pebble

Quartz (SiO₂), possibly quartzite or weathered granite fragment

Weathered, quartz-rich metamorphic rock (likely schist or gneiss)

Quartz–feldspar–mica schist/gneiss, with surface lichens and iron-oxide staining

Sandstone (Ferruginous)

Arenite (primarily SiO2 with Fe2O3 staining)

Turquoise

Turquoise - CuAl6(PO4)4(OH)8·4H2O

Banded Agate (specifically Eye Agate / Chalcedony)

Agate (Cryptocrystalline variety of Quartz, SiO2)

Riverstone (likely Graywacke or Siltstone)

Sedimentary sandstone (Graywacke), SiO2 dominant

Porphyritic Basalt

Basalt (Mafic Extrusive Igneous Rock)

Gray chalcedony (microcrystalline quartz)

Chalcedony, SiO₂; likely common gray/blue-gray variety

Conglomerate

Polymictic Conglomerate

Red-and-cream jasper

Jasper, an opaque microcrystalline variety of quartz (SiO₂), colored mainly by iron oxides

Carved quartz skull, likely smoky quartz or gray chalcedony

Silicon dioxide (SiO₂), quartz or microcrystalline quartz

Red Sandstone

Arenite (Ferruginous Sandstone)

Coquina

Bioclastic Limestone (Calcium Carbonate, CaCO3)

Citrine Quartz

Silicon Dioxide (SiO2) with iron impurities

Weathered quartz-rich river cobble, possibly quartzite

Quartzite (mostly microcrystalline SiO₂), tentatively identified

Mica-rich metamorphic rock, likely schist

Biotite–muscovite schist, possibly garnet-bearing

Painted Garden Rock

Coated Siltstone or Mudstone

Sandstone with Manganese Oxide Patina

Clastic Sedimentary Rock (primarily SiO2)

Vesicular Basalt or Scoria

Basalt (extrusive volcanic rock)

Granite

Phaneritic Igneous Rock (primarily Quartz, Feldspar, and Mica)

Rounded river pebble

Indeterminate; likely quartz-rich sandstone, chert, or weathered volcanic rock

Limonite Concretion

Hydrated Iron Oxide-Hydroxide, FeO(OH)·nH2O

Red Quartzite / River Siltstone

Quartzite (SiO2 with iron oxide inclusions)

Citrine

Citrine (Silicon Dioxide, SiO2)

Sandstone

Sandstone (lithified quartz arenite, arkose, graywacke, etc. depending on composition)

Quartz-rich hydrothermal ore rock, likely gold-bearing quartz vein

Milky quartz (SiO₂) with iron-oxide staining and probable sulfide minerals; host rock may be schist or altered granite

Travertine (Tufa)

Chemical Limestone (CaCO3)

Ocean Jasper

Orbicular Jasper / Chalcedony (SiO2)

Granite

Plutonic Igneous Rock (composed typically of SiO2, Al2O3, K2O, Na2O, CaO)

Banded Calcite (often sold as 'Mexican Onyx' or 'Green Onyx')

Calcite (Calcium Carbonate, CaCO3)

Aventurine

Aventurine Quartz (SiO2 with inclusions)

Weathered blue-gray calcite/aragonite fragment

Calcium carbonate (CaCO₃), probably calcite; possibly shell-derived aragonite

Petrified Wood

Silicified Wood (SiO2)

Pink Granite

Phaneritic Felsic Igneous Rock (composed primarily of K-Feldspar, Quartz, and Mica)

Quartz geode / iron-stained quartz vein rock

Quartz (SiO₂), likely with iron oxides and minor feldspar or host-rock minerals

Peacock Ore (Bornite or Chalcopyrite)

Bornite (Cu5FeS4) or Acid-Washed Chalcopyrite (CuFeS2)

Weathered porphyritic volcanic rock (likely andesite or basalt)

Aphanitic to porphyritic andesite–basalt; composition commonly plagioclase, pyroxene, and minor iron oxides

Banded Gneiss

Gneiss (Foliated Metamorphic Rock)

Magnetite (potentially as a Lodestone or within Ironstone)

Magnetite (Fe3O4)

Quartz Pebble

Silicon Dioxide (SiO2)

Quartzite Pebble

Metamorphic Quartz (SiO2)