Igneous Or Sedimentary

Pyrite

Iron Sulfide (FeS2)

Galena

Lead Sulfide (PbS)

Gneiss

Gneiss (High-grade Metamorphic Rock)

Gneiss

Gneiss

Gneiss

Gneiss

Banded gneiss pebble

Biotite–quartz–feldspar gneiss (composition variable)

Banded Gneiss

Gneiss (High-grade Metamorphic Rock)

Blue Chalcedony

Microcrystalline Quartz (SiO2)

Veined gneiss

Felsic to mafic banded gneiss, chiefly quartz–feldspar–biotite/hornblende

Polished gneiss or migmatitic gneiss cobble

Banded quartz–feldspar–biotite gneiss; compositionally possibly migmatitic

Banded gneiss (likely migmatitic gneiss)

Gneiss; quartz–feldspar–mica metamorphic rock, locally approaching migmatite

Banded gneiss pebble

Gneiss, typically quartz–feldspar–mica banded rock

Banded Gneiss

Gneiss (High-grade Regional Metamorphic Rock)

Banded Gneiss

Gneiss (Metamorphic Rock)

Banded gneiss pebble

Gneiss, chiefly quartz–feldspar–mica with dark biotite/amphibole bands

Quartz Geode

Silicon Dioxide (SiO2)

Agate

Silicon Dioxide (Chalcedony), SiO2

Banded metamorphic pebble, likely gneiss

Foliated gneiss; quartz–feldspar–mica assemblage

Gneiss

High-grade metamorphic rock (Gneiss)

Banded Gneiss

Gneiss (High-grade regional metamorphic rock)

Polished banded gneiss or schist pebble

Banded quartz–feldspar–mica gneiss (tentative)

Gneiss

Gneiss

Uncertain gray metamorphic rock, likely gneiss or schist

Quartz–feldspar–mica rock; exact identification requires close examination

Banded Gneiss

Gneiss (High-grade Metamorphic Rock)

Gneiss

Gneiss

Gneiss (with Quartz and Mica)

Gneiss

Gneiss

Metamorphic rock of high-grade regional metamorphism

Banded metamorphic rock, likely gneiss or foliated amphibolite

Quartz–feldspar–mica gneiss or amphibolite; exact identification requires testing

Foliated metamorphic rock, likely gneiss

Biotite–quartz–feldspar gneiss, possibly migmatitic gneiss

Tumbled magnetite (likely)

Magnetite, Fe₃O₄; possibly magnetite-rich ironstone

Turquoise

Hydrated phosphate of copper and aluminum - CuAl6(PO4)4(OH)8·4H2O

Weathered banded metamorphic rock, likely gneiss

Banded gneiss; commonly quartz–feldspar–mica assemblage

Banded metamorphic rock, likely gneiss

Biotite–quartz–feldspar gneiss (probable); exact identification requires testing

Carnelian / Chalcedony

Cryptocrystalline Quartz (SiO2)

Epidote

Epidote (Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH))

Gneiss

Foliated Metamorphic Gneiss

Likely banded gneiss or mica-rich metamorphic pebble

Gneiss; composition likely quartz, feldspar, and biotite/muscovite mica

Rough Agate/Chert Nodules

Cryptocrystalline Quartz (SiO2)

Gneiss

Gneiss

Banded Gneiss

Gneiss (High-grade regional metamorphic rock)

Gneiss (River Cobble)

Gneiss (Foliated Metamorphic Rock)

Banded Gneiss

Gneiss (Metamorphic rock of variable mineralogy, often quartz-feldspar base)