Mineral In A Matrix (Likely Quartz Or Feldspar)

Biotite Mica

K(Mg,Fe)3AlSi3O10(OH)2

Banded gneiss pebble

Gneiss, likely quartz–feldspar–mica gneiss

Weathered iron-rich sandstone or conglomeratic sedimentary cobble

Ferruginous sandstone, possibly polymictic conglomerate

Weathered porphyritic volcanic rock (likely rhyolite or andesite)

Porphyritic rhyolite–andesite; chiefly quartz/feldspar with iron-oxide-stained groundmass

Porphyritic Rhyolite

Porphyritic Rhyolite (Extrusive Igneous Rock)

Rounded conglomeratic river pebble

Polymict conglomerate (lithified gravel), composition uncertain from image

Tumbled pegmatitic rock, likely amazonite-bearing granite

Granite/pegmatite composed mainly of quartz, feldspar, and mica; blue-green area may be microcline (amazonite)

Rounded pebble, likely quartz-rich river stone

Indeterminate quartz-feldspar-rich lithology; possibly weathered granite or quartzite

Black-and-white banded pebble (likely gneiss or migmatite)

Undetermined banded metamorphic rock; mineral composition cannot be confirmed from the image

Biotite-rich schist

Mica schist, chiefly biotite mica with quartz and feldspar

Weathered sandstone or altered volcanic rock

Indeterminate; likely quartz–feldspar-rich sandstone, possibly tuff

Rounded, weathered rock (likely quartz-rich granite or gneiss)

Undetermined quartz–feldspar-rich rock; precise identification requires closer examination

Mica-rich metamorphic rock (likely schist)

Muscovite–biotite schist; predominantly phyllosilicate mica minerals in a quartz/feldspar matrix

Weathered sandstone fragment

Clastic sandstone, likely quartz-rich (quartz arenite or arkose)

Likely schist fragment

Mica schist, probably quartz–biotite schist

Pink sandstone or weathered sedimentary stone

Likely quartz-rich sandstone (lithified siliciclastic sediment)

Granite or Pegmatite in host rock

Granitoid / Felsic Intrusive Rock

Uncertain gray-and-white rock fragment

Likely quartz-bearing granite or quartzite; exact identification requires testing

Quartz-rich pegmatite, possibly with mica

Granite/pegmatite composed mainly of quartz (SiO₂), feldspar, and likely biotite or muscovite mica

Likely foliated metamorphic rock (schist or gneiss fragment)

Mica schist–gneiss; chiefly quartz, feldspar, and mica

Pegmatitic gneiss with a quartz–feldspar vein

Quartz–feldspar-rich gneiss, locally cut by a granitic pegmatite vein

Schist, possibly garnet-mica schist

Mica schist; chiefly muscovite/biotite mica, quartz, and feldspar, with possible garnet or sulfide grains

Quartz-bearing conglomeratic rock with orange feldspar/calcite inclusion

Probably porphyritic granite or granitic pegmatite; exact identification requires a thin section or tests

Veined gneiss

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

Quartz-bearing feldspar pegmatite (likely with mica/tourmaline)

Granitic pegmatite; chiefly quartz (SiO₂) and feldspar, with dark mica or tourmaline

Quartz-rich pegmatite with purple amethyst

Granite pegmatite; crystalline quartz (SiO₂), locally amethyst (purple quartz)

Quartz-bearing dark rock, possibly hornfels or basalt

Probable quartz–feldspar rock; exact identification requires testing

Weathered feldspar-rich pegmatite or granite outcrop

Quartz–feldspar granitoid, likely containing potassium feldspar (KAlSi₃O₈) and quartz (SiO₂)

Sandstone (likely Quartz Sandstone)

Arenite (SiO2 based)

Quartz–feldspar pegmatite with red hematite/stilbite-like crystals

Granitic pegmatite; chiefly quartz (SiO₂), feldspar, mica, and iron-oxide minerals, with possible zeolite-group crystals

Likely weathered gneiss or granite fragment

Quartz–feldspar–mica aggregate; probably granitoid gneiss, identification uncertain from the photograph

Granitic Quartz with Feldspar

Granite (composed primarily of SiO2 and KAlSi3O8)

Weathered Sandstone or Siltstone

Sedimentary Rock

Likely weathered granite or granitic gneiss

Quartz–feldspar–mica rock; possibly gneissic granite

Small quartz-rich rock fragment

Likely quartz-bearing granite, pegmatite, or quartzite; exact identification is uncertain from the photograph

White quartz in dark matrix (likely quartz-bearing breccia or polished composite specimen)

Quartz, SiO₂, in an unidentified dark silicate matrix

Rutile in matrix (likely quartz-bearing specimen)

Rutile, titanium dioxide (TiO₂), with quartz and possibly chlorite/mica matrix

Rounded metamorphic pebble, likely gneiss or mica schist

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

Small tumbled pebble (likely quartz or feldspar)

Indeterminate; probable quartz (SiO₂) or feldspar

Polished orbicular/porphyritic granite or breccia

Likely potassium-feldspar–quartz granite with amphibole/biotite and epidote; exact variety uncertain from the image

Rhyolite porphyry

Porphyritic rhyolite, a silica-rich volcanic rock; exact identification requires closer examination

Granite

Felsic intrusive igneous rock (Granite)