Igneous Or Sedimentary

Banded gneiss pebble

Gneiss, a foliated metamorphic rock, likely quartz–feldspar–mica gneiss

Druzy Quartz (on Geode Fragment)

Silicon Dioxide (SiO2)

Banded gneiss pebble

Gneiss, a foliated metamorphic rock composed mainly of quartz, feldspar, and mica or amphibole

Banded Gneiss

Gneiss (High-grade metamorphic rock)

Banded gneiss or banded metamorphic rock

Gneiss, likely quartz–feldspar–biotite gneiss

Gneiss

Foliated Metamorphic Rock (Gneiss)

Banded gneiss, possibly garnet-bearing

Foliated gneiss; predominantly quartz–feldspar–mica, with possible amphibole or garnet

Blue-dyed Quartz Druzy

Silicon Dioxide (SiO2) with artificial pigment

Amethyst

Amethyst (SiO2 - Silicon Dioxide with iron impurities)

Banded Gneiss

Gneiss (High-grade Regional Metamorphic Rock)

Brown Chalcedony (Agate/Jasper blend)

Silicon dioxide (SiO2)

Yellow Chalcedony (Carnelian/Yellow Agate)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Banded gneiss pebble

Gneiss, commonly quartz–feldspar–mica gneiss

Carnelian (Tumbled)

Carnelian (Chalcedony / Silicon Dioxide, SiO2)

Banded Gneiss

Gneiss (High-grade Regional Metamorphic Rock)

Gneiss with Quartz Vein

Gneiss (containing SiO2 vein)

Natural quartz crystal (likely herkimer-style quartz)

Quartz, silicon dioxide (SiO₂)

Banded gneiss

Gneiss, commonly quartz–feldspar–mica gneiss

Dendritic Opal (Common Opal)

Amorphous Hydrated Silica (SiO2·nH2O) with Manganese or Iron Oxide inclusions

Polished banded gneiss or amphibolite specimen

Biotite–quartz–feldspar gneiss, possibly amphibole-rich; exact identification requires testing

Banded gneiss pebble

Biotite–quartz–feldspar gneiss (composition variable)

Banded Gneiss

Gneiss (Metamorphic Rock)

Gneiss (specifically a weathered or stream-worn specimen)

Gneiss (Foliated Metamorphic Rock)

Gneiss

Gneiss (High-grade regional metamorphic rock)

Gneiss

Gneiss (High-grade metamorphic rock typically composed of Quartz, Feldspar, and Mica/Amphibole)

Banded Gneiss

Gneiss (Metamorphic high-grade rock)

Agate Geode

Chalcedony (SiO2 - Silicon Dioxide)

Banded gneiss pebble

Gneiss, likely quartz–feldspar–mica gneiss

Gneiss

Metamorphic Gneiss

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Quartz (Milky/Gravel variety)

Silicon Dioxide (SiO2)

River Cobble (Gneiss/Migmatite)

Gneissic Metamorphic Rock (composed mainly of Quartz, Feldspar, and Biotite)

Weathered gneissic metamorphic rock

Gneiss, likely quartz–feldspar–mica gneiss

Mixed river-worn rock and mineral collection

Mostly quartz/quartzite, feldspar-bearing granitoid, chert, and mafic volcanic rocks; exact species vary by pebble

Banded gneiss with amphibolite and granitic rocks

Gneiss, commonly quartz–feldspar–biotite gneiss; associated amphibolite and granite

Pink Opal / Peruvian Opal

Hydrated amorphous silicon dioxide (SiO2·nH2O)

Gneiss

Gneiss (High-grade metamorphic rock)

Pyrite

Pyrite (FeS₂)

Banded Rock (likely Quartz-rich)

Uncertain, likely a Metamorphic Rock (e.g., Gneiss or Schist) with prominent Quartz and other minerals

River Stone (Basalt or Siltstone with banding)

Polished Basaltic or Siliciclastic River Cobble

River Rocks (Basalt and Sedimentary Stones)

Mafic Igneous Rock (Basalt) and Clastic Sedimentary Rock

Mixed River Pebbles (including Unakite and Jasper)

Polymineralic geological specimens