Sedimentary Or Igneous Fragment

Basalt with Chert/Obsidian blade

Aphanitic Mafic Igneous Rock (Basalt) with Microcrystalline Silica (Chert)

Pyrite-bearing schist or quartzite

Micaceous quartz-rich metamorphic rock with pyrite (FeS₂)

Chert Breccia

Brecciated Chert

Weathered schist or gneiss boulder

Micaceous quartz-feldspar schist/gneiss; exact identification is limited by the photograph

Magnetite (Iron Ore)

Magnetite (Fe3O4)

Almandine Garnet

Almandine, Fe3Al2(SiO4)3

Quartz (with Sandstone/Quartzite rocks)

Silicon Dioxide (SiO2)

Exposed aggregate concrete (stone-chip surface)

Portland-cement concrete containing natural aggregate; not a natural rock

Silver-colored mica schist

Muscovite–quartz schist, possibly with biotite

Weathered granite pebble

Granite, a coarse-grained felsic intrusive igneous rock composed chiefly of quartz and feldspar with dark mica or amphibole

Rock crystal quartz fragment

Quartz (silicon dioxide, SiO₂)

Clear quartz crystal (likely quartz fragment)

Quartz, silicon dioxide (SiO₂)

Quartz-rich vein rock, likely milky quartz in weathered host rock

Milky quartz (SiO₂), probably with weathered feldspar and iron-oxide staining

Pyrite

Iron Sulfide (FeS2)

Unidentified translucent crystal/mineral fragment

Likely quartz (SiO₂), but visual identification is uncertain

Quartz (Smoky/Milky variety)

Silicon Dioxide (SiO2)

Quartz

Silicon Dioxide (SiO2)

Weathered volcanic rock, likely altered basalt/andesite

Fine-grained mafic to intermediate volcanic rock; possible chlorite–calcite alteration

Quartz (Iron-stained or Chalcedony varieties)

Silicon Dioxide (SiO2)

Mixed mineral and rock specimen collection

Mixed assemblage, visibly including quartz, chalcedony/agate, feldspar, mica, dark mafic rocks, and possibly calcite or gypsum

Iron-stained quartz-rich rock, possibly weathered granite or pegmatite

Quartz (SiO₂) with probable feldspar and iron-oxide staining; exact identification is uncertain from the photograph

Quartz crystal (likely clear quartz)

Quartz, silicon dioxide (SiO₂)

Conglomeratic concrete or asphalt aggregate surface with dark bituminous chunks

Polymictic gravel aggregate; dark pieces likely bitumen/asphalt, not a natural rock

Clear quartz crystal

Quartz (silicon dioxide, SiO₂), likely milky or included rock crystal

Fossil shell fragment

Indeterminate molluscan bioclast, likely aragonite or calcite

Flint (chert) fragment

Microcrystalline quartz (SiO₂), commonly called flint when dark

Polished fossiliferous limestone

Bioclastic limestone, chiefly calcite (CaCO₃)

Quartzite with Mica / Gneiss Pebble

Metamorphic Rock (Quartz-Feldspar-Mica aggregate)

Likely quartz-rich pebbles

Quartz (SiO₂), possibly milky quartz or quartzite; identification is uncertain from the blurry image

Mixed rock and mineral specimen collection

Mostly undetermined from the photograph; apparent quartz-rich rocks, sandstone, granite/gneiss, and possibly iron-oxide-bearing specimens

Generic Pebble

Lithic Fragment

Weathered quartz-rich rock, likely granite or pegmatite fragment

Granite/pegmatitic granitoid; chiefly quartz (SiO₂), feldspar, and minor mica or iron oxides

Gneiss

Gneiss

Small dark rock fragment (unidentified)

Undetermined; composition cannot be identified reliably from this photograph

Clear Quartz

SiO2 (Silicon Dioxide)

Quartz

Silicon Dioxide (SiO2)

Quartz (Common Quartz/Citrine-toned)

Silicon Dioxide (SiO2)

Gneiss

Gneiss (High-grade Regional Metamorphism)

Milky quartz

Quartz (silicon dioxide, SiO₂)

Small green stone, possibly serpentine or greenstone

Undetermined; serpentine minerals are generally Mg₃Si₂O₅(OH)₄

Uncertain—likely weathered granite or quartz-rich rock

Granite (quartz–feldspar–mica aggregate), tentative

Vesicular basalt (likely weathered scoria)

Basaltic volcanic rock; chiefly plagioclase, pyroxene, and iron-rich olivine