Metamorphic Rock

Banded metamorphic rock, likely gneiss or migmatitic gneiss

Quartz–feldspar–mica gneiss; exact identification requires a fresh surface and mineral tests

Coarse-grained metamorphic rock, likely gneiss

Biotite–quartz–feldspar gneiss (probable; exact identification requires a fresh surface and tests)

Blue-gray metamorphic rock, likely gneiss or schist

Quartz–feldspar–mica assemblage; exact identification requires testing

Quartz-rich metamorphic rock, possibly quartzite

Quartzite; primarily crystalline silicon dioxide (SiO₂), with minor feldspar, mica, or iron oxides

Dark gray metamorphic rock fragment

Likely slate or fine-grained schist; mineral composition cannot be confirmed from the image

Weathered quartz-rich metamorphic rock, likely gneiss

Quartz–feldspar–mica gneiss; exact identification requires thin-section or chemical testing

Likely garnet-bearing metamorphic rock

Garnet amphibolite or garnet-bearing schist; chiefly almandine garnet (Fe₃Al₂Si₃O₁₂) with amphibole, mica, and quartz

Raw garnet-rich metamorphic rock

Likely garnet-bearing schist or garnetite; garnet-group silicates, commonly almandine (Fe₃Al₂Si₃O₁₂)

Dark, mica-rich metamorphic rock (possibly schist)

Mica schist, tentatively; exact identification is limited by the small, partly obscured specimen

Weathered quartz-rich metamorphic rock, possibly gneiss or quartzite

Quartz–feldspar–mica metamorphic aggregate; exact identification requires testing

Dark coarse-grained metamorphic rock, likely amphibolite or hornblende schist

Amphibolite, dominated by hornblende amphibole and plagioclase feldspar; exact identification requires testing

Weathered quartz-rich metamorphic rock (likely quartzite)

Quartzite, predominantly microcrystalline quartz (SiO₂), with possible feldspar, mica, and iron-oxide staining

Quartz-rich metamorphic rock, likely quartzite

Quartzite; predominantly microcrystalline quartz (SiO₂), with possible feldspar, mica, and iron-oxide staining

Coarse-grained metamorphic rock, likely gneiss

Granitic gneiss; typically quartz + feldspar + biotite/hornblende

Quartz-rich metamorphic rock, likely mica schist

Mica schist; chiefly quartz (SiO₂) with biotite/muscovite mica and possible feldspar

Banded metamorphic rock, likely gneiss

Biotite–quartz–feldspar gneiss, possibly migmatitic

Likely garnet-bearing metamorphic rock

Possibly garnetiferous mica schist; exact identification requires close examination or testing

Mica-rich metamorphic rock, likely phyllite or mica schist

Muscovite- and/or biotite-bearing schist/phyllite; exact identification requires testing

Foliated metamorphic rock, likely schist

Mica schist or chlorite schist; composition commonly quartz + mica/chlorite ± feldspar

Weathered gray-green metamorphic rock, likely serpentinite or altered basalt

Serpentinite, chiefly serpentine-group minerals (antigorite/lizardite); identification is provisional from the photograph

Coarse-grained metamorphic rock, likely amphibolite or hornblende gneiss

Amphibolite; predominantly hornblende amphibole and plagioclase feldspar, possibly with quartz and biotite

Dark gneiss or banded metamorphic rock

Banded quartz–feldspar–mica gneiss; exact identification requires testing

Weathered quartz-rich metamorphic rock

Likely quartzite or quartz-veined schist; primarily SiO₂ with possible mica, feldspar, and iron oxides

Pyrite-bearing metamorphic rock (likely pyrite schist or quartz–pyrite ore)

Pyrite (FeS₂) in a quartz–mica-rich matrix; exact host rock is uncertain from the image

Gray foliated metamorphic rock, likely gneiss or schist

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

Weathered iron-rich metamorphic rock (probable amphibolite or schist fragment)

Likely hornblende–plagioclase amphibolite with biotite/chlorite alteration; exact identification requires testing

Quartz-rich metamorphic rock (likely quartzite)

Quartzite, composed mainly of quartz (SiO₂); exact identification is uncertain from the photo

Green-brown metamorphic rock, possibly serpentinite

Serpentinite, chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), with possible magnetite, chlorite, or carbonate

Dark metamorphic rock, likely schist or phyllite

Micaceous schist/phyllite; commonly quartz, mica, and feldspar

Quartz-rich metamorphic rock, likely milky quartzite

Quartzite; predominantly quartz (SiO₂), with minor mica, feldspar, and iron-oxide staining

Quartz-rich metamorphic rock, likely quartzite

Quartzite; predominantly quartz (SiO₂), with minor iron-oxide and mica impurities

Quartz-rich metamorphic rock (probable quartzite)

Quartzite; predominantly crystalline SiO₂, with possible mica and iron-oxide impurities

Weathered mica-rich metamorphic rock

Likely schist or phyllite; composition probably quartz, mica, and feldspar

Banded quartz-rich metamorphic rock (likely quartzite or quartz-mica schist)

Quartzite/schist composed chiefly of SiO₂ quartz with mica, feldspar, and iron-oxide or copper-colored accessory minerals

Quartz-rich metamorphic rock, likely quartzite

Quartzite; predominantly microcrystalline quartz (SiO₂), possibly with mica or feldspar

Weathered quartz-rich metamorphic rock, likely gneiss or quartzite

Quartz (SiO₂)-bearing gneiss; exact identification requires a fresh surface and tests

Likely gneiss (banded metamorphic rock)

Felsic-to-intermediate gneiss; exact mineral identification requires closer examination

Banded metamorphic rock, likely gneiss

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

Quartz–feldspar–mica metamorphic rock, likely gneiss

Gneiss; composition commonly quartz (SiO₂), feldspars, biotite/hornblende, and minor accessory minerals

Foliated metamorphic rock, likely gneiss

Biotite–quartz–feldspar gneiss (provisional identification)

Quartz-rich metamorphic rock, likely quartzite

Quartzite; predominantly microcrystalline quartz (SiO₂), with minor feldspar, mica, and iron-oxide staining

Polished garnet-bearing metamorphic rock

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