Sedimentary Or Igneous Fragment

Quartz Pebble

Quartz (Silicon Dioxide, SiO2)

Likely weathered brown rock fragment

Indeterminate; possibly basaltic or iron-stained mafic rock

Granite

Phaneritic Felsic Intrusive Igneous Rock

Likely obsidian (black volcanic glass)

Obsidian; predominantly rhyolitic volcanic glass, often ~70–75% SiO₂

Weathered granite or granitic rock fragment

Granite; chiefly quartz, feldspar, and mica (composition uncertain from image)

K-Feldspar Granite Fragment

Granite (Alkali Feldspar-rich)

Fossiliferous Limestone

Limestone with fossil inclusions (CaCO3)

Rock Fragment with Calcite/Quartz Vein

Polymictic Rock Fragment (SiO2 / CaCO3)

Granitic Gneiss

Gneiss (containing Potassium Feldspar and Quartz)

White Quartz

Silicon Dioxide (SiO2)

Quartz (Druzy)

Silicon Dioxide (SiO2)

Gneiss

Gneiss (Foliated Metamorphic Rock)

Chalcedony with Quartz Crystals

Silicon Dioxide (SiO2)

Quartz Geode Fragment

Crystalline Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2) within Sedimentary or Igneous host

Unidentified weathered rock fragments

Likely mixed silicate rocks; specific identification requires testing

Amethyst (Geode Fragment)

Silicon Dioxide with iron impurities (SiO2)

Quartz (Milky Quartz)

Silicon Dioxide (SiO2)

Small quartz-rich rock fragment (tentative)

Quartz, silicon dioxide (SiO₂), possibly in a feldspar-bearing granite fragment

Quartz Vein in Host Rock

Silicon Dioxide (SiO2) within Sedimentary or Igneous Matrix

Mixed River Pebbles

Clastic Sedimentary Alluvial Deposit / Polymictic Conglomerate Clasts

Blue-and-gold lapis lazuli fragment

Lapis lazuli; lazurite-rich calc-silicate rock (primarily lazurite, with calcite and pyrite)

Weathered granitic rock fragment

Likely granite or granodiorite, composed mainly of quartz, feldspar, and mica

Calcite (likely honey/orange calcite)

Calcite — calcium carbonate, CaCO₃

Weathered sandstone or iron-stained limestone fragment

Likely quartz-rich sandstone (SiO₂) or calcitic limestone (CaCO₃); exact identification requires testing

Quartz (Clear or Milky)

Silicon Dioxide (SiO2)

Likely petrified wood or silicified fossil fragment

Silicified wood; predominantly microcrystalline quartz (SiO₂)

Bivalve Fossil (Shell Fragment)

Class Bivalvia (Calcium Carbonate - CaCO3)

Magnetite

Magnetite (Fe3O4)

Quartz (Milky/Clear variety)

Silicon Dioxide (SiO2)

Conglomerate

Conglomerate (SiO2 matrix with various silicate clasts)

Chert (Green variety)

Silicon Dioxide (SiO2)

Chert (often called Flint)

Microcrystalline Quartz (SiO2)

Quartz

Silicon Dioxide (SiO2)

Granite or granitic pegmatite fragment

Felsic intrusive rock, chiefly quartz, feldspar, and mica

Quartz

Silicon Dioxide (SiO2)

Granite Sand (Decomposed Granite)

Grus / Quartz-Feldspar Detritus

Quartz (Crystal)

Silicon Dioxide (SiO2)

Pyrite (Fool's Gold)

Iron Sulfide (FeS2)

Quartz

Silicon Dioxide (SiO2)

Weathered sandstone or limestone fragment

Likely quartz-rich sandstone or calcitic limestone; exact identification is uncertain from the image

Conglomerate

Clastic sedimentary rock (Conglomerate)