Mineral In A Matrix (Likely Quartz Or Feldspar)

Amethyst cluster

Quartz, silicon dioxide (SiO₂), purple variety

Porphyritic granite (weathered granitic rock)

Granite, likely biotite–hornblende porphyritic granite

Concrete-like aggregate surface with embedded rock fragments

Anthropogenic concrete or exposed aggregate; not a natural rock specimen

Quartz-rich pegmatite or quartz vein rock

Mostly quartz (SiO₂), with probable feldspar and iron-oxide staining

Biotite-rich granite or granitic gneiss

Quartz–feldspar–biotite granite; possibly weakly foliated gneiss

Likely weathered quartz-bearing rock

Indeterminate; possibly quartz-rich granite or granitic pegmatite

Basalt with Quartz/Calcite Vein

Basalt (Mafic Volcanic Rock with secondary mineralization)

Porphyritic volcanic rock, likely rhyolite or andesite

Porphyritic rhyolite/andesite; phenocrysts in a fine-grained volcanic groundmass

Tourmaline-bearing pegmatite

Quartz–feldspar pegmatite with black schorl tourmaline; minor mica likely present

Weathered gray sandstone or siltstone

Clastic sedimentary rock, likely quartz–feldspar-rich sandstone/siltstone

Porphyritic Igneous Rock / Rhyolite Porphyry

Porphyritic volcanic rock

Raw quartz-rich rock fragment

Quartz (SiO₂), likely iron-stained quartz or quartz-bearing feldspathic material

Epidosite with Quartz (Unakite-variant or Jasper)

Epidotized Metasomatite

Pyrite in Matrix (likely Quartz or Schist matrix)

Iron Sulfide (FeS2)

Pegmatitic granite (likely feldspar–quartz–mica rock)

Granitic pegmatite; chiefly K-feldspar and quartz, with mica and iron-oxide staining

Rounded river pebbles, likely quartz-rich sandstone or quartzite

Indeterminate quartz–feldspar rock; possible quartzite or arkosic sandstone

Milky quartz with possible mica or feldspar inclusions

Quartz (SiO₂), likely with minor inclusions

Rose Quartz attached to matrix

Silicon dioxide, SiO2

Basalt with Quartz/Feldspar Inclusions

Amygdaloidal or Porphyritic Mafic Volcanic Rock with Siliceous Veining

Granitic Gneiss

Gneiss (containing Potassium Feldspar and Quartz)

Unidentifiable embedded dark fragment

Indeterminate; possibly a dark silicate mineral or lithic inclusion

Likely garnet-bearing metamorphic rock

Garnet-rich schist or gneiss; garnet is commonly almandine, Fe₃Al₂(SiO₄)₃

Small pink mineral fragment

Indeterminate; possibly rose quartz or feldspar

Quartz-rich breccia or pegmatitic granite fragment

Quartz–feldspar rock; possibly hydrothermal quartz breccia

Conglomerate (rounded-pebble rock)

Lithified polymictic conglomerate; clasts cemented by a finer mineral matrix

Flecked granite pegmatite

Granitic rock composed mainly of quartz, alkali feldspar, plagioclase, and dark biotite/amphibole

Polymictic conglomerate (possibly impact breccia)

Lithified polymictic conglomerate/breccia; clasts appear mainly mafic volcanic rock, with quartz- or feldspar-rich fragments in a dark matrix

Granitic Quartz (with Feldspar inclusions)

Quartz (SiO2) with Potassium Feldspar (KAlSi3O8)

Tourmaline-bearing pegmatite (likely black schorl in a pale quartz/feldspar matrix)

Schorl tourmaline, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄, with quartz and feldspar

Pegmatite (Granitic) with Tourmaline

Granitic Pegmatite (containing Schorl and Quartz)

Smoky quartz in matrix

Quartz, silicon dioxide (SiO₂), smoky variety

Likely quartz-bearing rock fragment

Quartz (SiO₂), possibly in a weathered granitoid or metamorphic matrix

Rounded gray pebble, likely quartz-rich river cobble

Probable granitic or quartzitic cobble; exact identification requires a fresh surface and tests

Granite or Porphyritic Igneous Rock (weathered)

Granitoid

Banded gneiss (likely amphibolite-bearing gneiss)

Gneiss; quartz–feldspar–mica/amphibole aggregate

Porphyritic granitic rock (likely orbicular granite or granite porphyry)

Granite/granodiorite, chiefly quartz (SiO₂), feldspar, and dark biotite or hornblende

Granite Pebble

Granite (Phaneritic Igneous Rock)

Quartz-bearing pegmatite fragment

Granitic pegmatite; chiefly quartz (SiO₂), with probable feldspar and dark mica/amphibole

Copper-bearing metamorphic rock, likely bornite- or chalcopyrite-rich schist

Quartz–mica schist with disseminated copper sulfides; possible bornite (Cu₅FeS₄) and chalcopyrite (CuFeS₂)

Blue-green beryl, likely aquamarine in quartz or feldspar matrix

Beryl, Be₃Al₂Si₆O₁₈; the blue-green variety is aquamarine

Gneiss

Quartz–feldspar–mica gneiss

Weathered quartz-bearing rock, possibly gneiss or quartzite

Indeterminate; likely quartz-rich metamorphic rock containing quartz and feldspar