Mineral In A Matrix (Likely Quartz Or Feldspar)

Andesite Porphyry

Andesite (Intermediate Volcanic Rock)

Feldspathic Gneiss

High-grade Metamorphic Rock (Gneiss)

Quartzite

Quartzite (primarily SiO2)

Tumbled Granite

Granite (Felsic intrusive igneous rock)

River Pebble (likely Quartzite or Basalt)

Quartzite (SiO2 as primary mineral)

Weathered brown stone, likely sandstone or iron-stained granite

Indeterminate; possible quartz-rich sandstone (quartz, feldspar, iron oxides)

Porphyritic Rhyolite

Rhyolite (Porphyritic texture)

Weathered tan mineral/rock fragment

Indeterminate from image; possibly iron-stained quartz, feldspar-rich rock, or limonite-bearing material

Unidentified gray weathered rock

Possibly weathered granite or granitic gneiss; exact identification requires a fresh surface and tests

Amazonite

Potassium Feldspar (KAlSi3O8)

Rounded granitic pebble

Granite, mainly quartz, feldspar, and biotite/hornblende

Granite Pebble

Granite (Phaneritic intrusive igneous rock)

Dalmatian Jasper

Peralkaline Quartz-Feldspar Igneous Rock

Granite with Orthoclase and Hematite Staining

Phaneritic Felsic Igneous Rock (primarily SiO2 with KAlSi3O8)

Weathered rhyolite or felsic volcanic rock

Rhyolite, commonly quartz–alkali feldspar–plagioclase with iron-oxide alteration

Weathered granite-like rock fragments

Granite or granodiorite; chiefly quartz, feldspar, and biotite/hornblende

Granite Pebble

Granite (Phaneritic Quartz-Feldspar intrusive rock)

Weathered pink granite cobble

Granite, likely biotite-bearing pink granite; exact variety cannot be confirmed from a photograph

Granite

Phaneritic Plutonic Felsic Rock (SiO2 > 69%)

Granite

Plutonic Intrusive Igneous Rock (Granite)

Quartz-rich stone, likely milky quartz

Quartz (silicon dioxide, SiO₂), possibly iron-stained or feldspar-bearing

Greenschist (or Serpentinite) with Quartz-Feldspar Vein

Metabasalt / Greenschist Facies Rock

Pink granite pebble

Granite, chiefly quartz, feldspar, and mica

Quartz Geode

Crystalline Silicon Dioxide (SiO2) in sedimentary matrix

Rhyolite (likely porphyritic)

Rhyolite; chiefly quartz, alkali feldspar, plagioclase, and volcanic glass, with possible iron-oxide staining

Felsic gneiss, likely granitic gneiss

Quartz–feldspar–mica gneiss; commonly quartz + plagioclase/K-feldspar + biotite or hornblende

Biotite-bearing granite or granodiorite

Coarse-grained felsic intrusive rock; primarily quartz (SiO₂), feldspar, and biotite mica, possibly with hornblende

Granite Pebble

Phaneritic Felsic Igneous Rock

Banded metamorphic rock, likely gneiss

Biotite–quartz–feldspar gneiss, possibly amphibolite-bearing

Amazonite (or Amazon Stone)

Potassium Feldspar (Microcline), K(AlSi3O8)

Sodalite in Feldspar (or Sodalite Syenite / Yooperite-type rock)

Na8(Al6Si6O24)Cl2 (Sodalite) with KAlSi3O8 (Feldspar)

Jasper-bearing Quartzite River Cobble

Tectonized Quartzite with Iron-Oxide (Hematite/Limonite) Veining

Zebra Jasper (with Chlorite/Epidote)

Silicon Dioxide (SiO2) with inclusions

Porphyritic Andesite

Andesite (Porphyry)

Porphyritic Basalt (or Andesite) Pebble

Porphyritic Mafic Volcanic Rock

Weathered mineralized rock fragment

Indeterminate; likely quartz–feldspar-rich lithic material with iron-oxide staining

Granite (Core Sample)

Phaneritic Felsic Igneous Rock (Granite)

Granite

Felsic Plutonic Rock (primarily SiO2)

Raw quartz-rich rock, likely milky quartz

Quartz (silicon dioxide, SiO₂), possibly quartzite or a quartz-bearing host rock

Granite or granitic gneiss

Felsic granitoid, chiefly quartz, feldspar, and mica; possibly weakly foliated gneiss

Pink quartz-rich stone, likely rose quartz

Rose quartz; quartz, SiO₂, commonly colored by trace elements and microscopic inclusions

Pink Granite

Phaneritic intrusive igneous rock (rich in Potassium Feldspar)