Sedimentary Or Igneous Fragment

Quartz-rich rock, possibly milky quartz or quartzite fragment

Quartz (SiO₂), potentially quartzite if metamorphic

Coarse Sand Grain / Lithic Fragment

Clastic Sediment (Lithic fragment or Quartz/Feldspar grain)

Quartz-veined Metamorphic Pebble

Silicate-rich metamorphic rock with quartz veins (SiO2)

Black tourmaline (schorl), probable

Schorl tourmaline, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

Quartz

Silicon Dioxide (SiO2)

Geode

Silicon Dioxide (Quartz/Chalcedony) in carbonate or volcanic host rock

Small white crystalline mineral fragment

Indeterminate; possibly calcite or quartz

Likely tumbled quartz or calcite

Quartz (SiO₂) or calcite (CaCO₃); exact identification requires hardness and acid tests

Opal

Hydrated Silica (SiO2·nH2O)

Gneiss

Gneiss

Dark metamorphic rock, likely biotite schist or gneiss

Quartz–feldspar–biotite metamorphic rock; exact identification requires a fresh surface and testing

Quartz-bearing metamorphic rock, likely schist or quartzite

Quartz (SiO₂) in a mica-rich metamorphic matrix

Quartz Geode Fragment

Silicon Dioxide (SiO2)

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

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

Small translucent quartz fragment

Quartz (SiO₂), possibly milky or near-colorless quartz

Weathered quartz-bearing metamorphic rock, likely gneiss or quartzite

Quartz-rich gneiss/quartzite with feldspar, mica, and iron-oxide alteration

Clear quartz fragment

Quartz (silicon dioxide, SiO₂)

Weathered iron-rich stone, likely basalt or ironstone

Indeterminate; possibly vesicular basalt (plagioclase–pyroxene) or ferruginous sandstone/ironstone

Asphalt aggregate

Human-made bituminous asphalt containing crushed silicate rock aggregate

Uncertain small stone; possibly weathered quartz-bearing rock

Indeterminate from image; candidate materials include quartz-rich pebble or altered silicate rock

Quartz-rich mineral fragment

Quartz (silicon dioxide, SiO₂), possibly milky quartz

Small quartz fragment

Quartz (silicon dioxide, SiO₂), possibly milky quartz

Quartz-rich rock fragment

Milky quartz, primarily silicon dioxide (SiO₂), possibly quartzite or a feldspar-bearing vein rock

Banded Gneiss

Gneiss

Weathered rock fragment (likely granite or quartz-rich sandstone)

Uncertain; possible granitic fragment containing quartz and feldspar

Quartz (Milky/Clear Quartz)

Silicon Dioxide (SiO2)

Garnet-bearing gneiss

Biotite–garnet gneiss, typically quartz + feldspar + biotite + almandine garnet

Common Quartz Pebble

Silicon dioxide (SiO2) rock fragment

Small white quartz fragment

Quartz (silicon dioxide, SiO₂)

Likely raw garnet fragment

Garnet-group silicate, commonly almandine (Fe₃Al₂Si₃O₁₂)

Concrete or asphalt-like aggregate surface with a dark fragment

Uncertain; likely artificial concrete containing mixed lithic aggregate, not a natural rock

Likely weathered metamorphic rock (possibly schist or gneiss)

Indeterminate; probable mica-rich quartz–feldspar metamorphic rock

Banded Gneiss Pebble

Gneiss (Metamorphic Rock)

Banded sandstone

Quartz-rich sandstone (quartz arenite or feldspathic sandstone; exact type cannot be determined from the image)

Mixed rough mineral specimens, likely quartz-bearing rocks

Probable quartz (SiO₂), with possible feldspar, iron oxides, and altered host rock

Weathered granitic rock

Granite, chiefly quartz + feldspar + mica; possibly a pale granodiorite

Colorless quartz crystal (likely quartz fragment)

Quartz, silicon dioxide (SiO₂)

Milky quartz (likely quartz vein fragment)

Quartz, silicon dioxide (SiO₂)

Quartz

Silicon Dioxide (SiO2)

Banded Gneiss / Metamorphic River Pebble

Gneiss (Foliated Metamorphic Rock)

Milky quartz fragment

Quartz (silicon dioxide, SiO₂)

Likely raw mica-bearing metamorphic rock or mineral fragment

Tentatively biotite schist; visually similar dark mica-rich material