Mineral In A Matrix (Likely Quartz Or Feldspar)

Sunstone

Plagioclase Feldspar (Na, Ca)(Al, Si)4O8 with Hematite or Copper inclusions

Potassium Feldspar and Quartz

KAlSi3O8 (Potassium Feldspar) and SiO2 (Quartz)

Sandstone

Sedimentary Clastic Rock (Quartz Arenite)

Quartz-bearing granite or granitic gneiss cobble

Granite; primarily quartz (SiO₂), feldspar, and mica/amphibole

Granite or granitic pegmatite fragment

Felsic intrusive rock, chiefly quartz, feldspar, and mica

Granite

Phaneritic Felsic Igneous Rock

Tiny amber-colored crystal fragment

Indeterminate; possibly quartz, feldspar, mica, or a sulfide mineral

Quartz Crystal Cluster

Silicon Dioxide (SiO2)

Breccia Pebble

Sedimentary Breccia

Copper-bearing Quartz (likely Malachite on Quartz matrix)

Cu2CO3(OH)2 (Malachite) on SiO2 (Quartz)

Weathered quartz-rich rock, possibly quartzite or quartz vein material

Quartz (SiO₂), likely with feldspar, mica, and iron-oxide staining

Granite (Weathered/Oxidized)

Phaneritic Felsic Igneous Rock (composed of Quartz, Orthoclase Feldspar, and Mica)

Weathered granite or granitic gneiss

Quartz–feldspar–mica granitoid; possibly weakly gneissic

Quartz on Schist

Silicon Dioxide (SiO2) on Foliated Metamorphic Rock

Weathered sulfide-bearing ore specimen

Likely pyrite- and/or chalcopyrite-bearing quartz–iron-oxide rock; exact identification requires testing

Weathered granitic rock, likely granodiorite

Granodiorite: quartz, plagioclase feldspar, potassium feldspar, and biotite/hornblende

Chinese Writing Stone

Porphyritic Basalt or Andesite with Feldspar phenocrysts (likely Orthoclase or Plagioclase)

Banded Gneiss (with possible weathered sulfide or iron staining)

Gneiss, potentially with iron oxide/hydroxide staining (e.g., limonite) or weathered sulfides

Granite cobble

Granite

Rounded gray metamorphic rock, likely quartzite or gneiss

Quartz-rich metamorphic rock; exact identification is uncertain from the photograph

Granite

Felsic intrusive igneous rock (Granite)

Banded Gneiss with Quartz Veining

Gneiss (High-grade Regional Metamorphism)

Graphic Granite

Pegmatitic Feldspar and Quartz (Graphic Granite)

Weathered quartz-rich rock, likely milky quartz or quartzite

Quartz (SiO₂), possibly quartzite with iron-oxide staining

Iron-stained quartz-rich rock, possibly gold-bearing quartz

Quartz (SiO₂) with iron-oxide staining; possible limonite/goethite matrix

Amazonite

Microcline (KAlSi3O8)

Tumbled pegmatitic granite

Granite, chiefly quartz–feldspar–mica; likely altered pegmatite

Chert with Druzy Quartz Geode

Microcrystalline Quartz (SiO2)

Likely weathered quartz-rich rock, possibly smoky quartz or chert

Quartz (SiO₂), though exact identification is uncertain from the photograph

Granitoid Pebble (Graphic Granite/Pegmatite)

Pegmatitic Granite with Quartz and Orthoclase

Granite Pebble

Granite

Banded gneiss (weathered glacial erratic)

Gneiss; typically quartz–feldspar–biotite ± hornblende

Rounded sandstone pebble

Quartz-rich sandstone; commonly arkose or lithic sandstone

Pink Granite

Phaneritic Felsic Igneous Granite

Granite with Biotite Inclusions

Intrusive Igneous Rock (Quartz, Feldspar, Biotite)

Pegmatitic Granite

Granite (composed of Quartz, Feldspar, and Mica)

Weathered granite pebble

Granite, mainly quartz, feldspar, and mica; approximate composition SiO₂-rich continental crust

Granitoid (Granite/Diorite)

Course-grained Plutonic Igneous Rock

Quartz with Feldspar and Mica (Pegmatite Fragment)

Granitic Pegmatite

Weathered sandstone or iron-stained sedimentary pebble

Quartz-rich sandstone; exact identification requires a fresh surface and tests

Pink Granite

Phaneritic Coarse-Grained Granite

Weathered granite or granitic pegmatite fragment

Granite, primarily quartz, alkali feldspar, and plagioclase; exact identification is limited by the photograph