Mineral In A Matrix (Likely Quartz Or Feldspar)

Tumbled gray-blue stone, likely quartz-rich feldspar or granite pebble

Probable granitic fragment: quartz (SiO₂) with feldspar and minor mica; exact identification requires testing

Granite or granitic gneiss

Coarse quartz–feldspar–mica rock; possible gneissic variant

Quartzite and Milky Quartz River Pebbles

Silicon Dioxide (SiO2)

Small rounded pebble, possibly quartz-rich stone

Indeterminate from image; likely quartz-bearing silicate rock

Black Tourmaline (Schorl) on Quartz

NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH)

Gneiss, likely migmatitic or granitic gneiss

Banded quartz–feldspar–mica gneiss; composition chiefly quartz, alkali/plagioclase feldspar, biotite and accessory minerals

Quartz with Inclusions

Silicon Dioxide (SiO2) with various mineral inclusions

Mica-rich schist (likely biotite schist)

Biotite–quartz–feldspar schist; mica is chiefly biotite, K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂

Quartz-rich pegmatite (likely feldspar–quartz rock)

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

Weathered mafic rock fragment

Likely basalt or volcanic breccia; identification is uncertain from the photograph

Quartz-rich granitoid pebble, likely granite or granitic gneiss

Granite: quartz + feldspar (orthoclase/plagioclase) + minor mica; possibly gneiss if foliated

Likely banded metamorphic rock, possibly schist or gneiss

Micaceous schist/gneiss; identification is limited from the photograph

Banded gneiss (likely biotite-rich gneiss)

Gneiss; chiefly quartz, feldspar, biotite, and possibly hornblende

Polished porphyritic volcanic pebble

Likely porphyritic basalt or andesite; exact identification requires a fresh surface and mineral tests

Granite (likely)

Granite, a coarse-grained felsic intrusive igneous rock composed mainly of quartz, feldspar, and mica

Tumbled quartz-rich stone, likely milky quartz

Quartz (SiO₂), possibly iron-stained milky quartz or quartzite

Granite-like igneous rock

Likely medium-grained granite or granodiorite; quartz–feldspar–mica aggregate

Tumbled granitoid pebble, likely granite

Granite: chiefly quartz, potassium feldspar, plagioclase, and dark biotite or amphibole

Garnet-bearing gneiss

Biotite–feldspar gneiss with almandine garnet; quartz likely present

Likely quartz-bearing rock or mineral fragment

Indeterminate; possibly quartz (SiO₂) with iron-oxide staining and darker matrix

Quartz geode/druse specimens

Quartz, silicon dioxide (SiO₂), likely iron-stained drusy quartz in a vuggy host rock

Sandstone Pebble

Sandstone (Silicon dioxide-rich clastic sedimentary rock)

Weathered quartz-rich rock, likely granite or granitic gneiss

Granite (quartz–feldspar–mica aggregate), possibly weathered granitic gneiss

Graphic Granite

Graphic Granite (a variety of Pegmatite)

Quartz crystal cluster on matrix

Quartz (silicon dioxide, SiO₂), likely iron-stained or included variety

Quartz-rich geode or druzy quartz

Quartz (SiO₂), possibly in a chalcedony/geode matrix

K2 Jasper (K2 Stone)

Azurite in Granite / Quartzite

Quartz-veined metamorphic rock, likely greenschist or altered metavolcanic

Chlorite–actinolite–epidote-bearing metavolcanic rock with quartz veins; exact identification requires testing

Schorl (Black Tourmaline) in Quartz/Feldspar Matrix

NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH)

Quartz pebble in concrete

Quartz (SiO₂), embedded in Portland-cement concrete

Rounded gray pebble, likely granite or granitic gneiss

Probable quartz–feldspar–mica aggregate; exact identification is limited by the blurred image

Likely mica schist

Mica-rich schist, probably biotite–quartz–feldspar schist

Likely pink granite

Granite, a coarse-grained felsic intrusive igneous rock, typically quartz + feldspar + mica

Feldspar-rich granite or granitic gneiss

Granite; mainly quartz (SiO₂), feldspar, and mica

Raw pink feldspar (likely orthoclase or microcline)

Potassium feldspar, KAlSi₃O₈

Weathered granite or granitic gneiss cobble

Quartz–feldspar–mica granitoid; exact identification requires a fresh surface or testing

Tumbled quartz-rich stone, possibly druzy quartz or quartzite

Quartz (SiO₂), likely in a quartzite or chalcedonic matrix

Weathered granite or granitic gneiss fragment

Granite; chiefly quartz, feldspar, and mica

Tumbled amazonite (likely)

Amazonite, green microcline feldspar (KAlSi₃O₈)

Weathered quartz-rich rock, possibly granite or quartzite

Indeterminate; likely quartz–feldspar aggregate, possibly altered granite

Likely granite

Granite, a quartz–feldspar-rich intrusive igneous rock

Likely quartz or quartz-rich pebble

Quartz (SiO₂), possibly milky quartz or a small quartzite fragment