Sedimentary Or Igneous Fragment

Rounded quartz-rich river pebbles

Alluvial gravel; commonly quartzite, chert, and quartz-bearing sandstone fragments

Decorative mosaic cross containing mixed rock and glass fragments

Polychrome aggregate; likely quartz, feldspar, marble, granite, and assorted colored glass

Flint (chert)

Microcrystalline quartz, SiO₂

Clear calcite cleavage fragment

Calcite (calcium carbonate, CaCO₃)

Milky quartz

Quartz (SiO₂), commonly called milky quartz

Granite (likely weathered granitic rock)

Granite; chiefly quartz (SiO₂), feldspar, and mica

Small dark-brown mineral pebble, identity uncertain

Not identifiable from the image; possibilities include iron-rich minerals such as magnetite or hematite

Pebble

Lithic fragment / Rounded rock fragment

Fossil shell fragment in sedimentary rock

Indeterminate marine mollusk shell; likely a bivalve or gastropod fossil

Biotite Mica (or Tourmaline fragment)

K(Mg,Fe)3AlSi3O10(F,OH)2

Yellow-green serpentine (likely)

Serpentine-group phyllosilicate, commonly lizardite or antigorite; approximate formula Mg₃Si₂O₅(OH)₄

Rounded metamorphic pebble, likely mica schist or gneiss

Mica schist/gneiss; commonly quartz, feldspar, and biotite or muscovite mica

Weathered metamorphic rock, likely mica schist or gneiss

Quartz–feldspar–mica schist/gneiss; exact identification is uncertain from the photograph

Porphyritic volcanic rock, likely andesite or rhyolite

Porphyritic andesite–rhyolite; chiefly plagioclase, quartz, and altered ferromagnesian minerals in a fine groundmass

Clear Quartz

Silicon Dioxide (SiO2)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Quartz Vein / Milky Quartz

Silicon Dioxide (SiO2)

Small quartz fragment (probable)

Quartz, SiO₂

Likely clear quartz fragment

Quartz (silicon dioxide, SiO₂)

River Pebble (Gneiss / Granitic Schist)

Metamorphic Rock (Quartz-Feldspar-Mica assembly)

Likely foliated metamorphic rock (quartz-mica schist or gneiss)

Quartz–feldspar–mica metamorphic rock; exact identification requires a fresh surface and tests

Garnet-bearing metamorphic rock, likely garnet schist or amphibolite

Almandine garnet (Fe₃Al₂Si₃O₁₂) in mica- or amphibole-rich matrix

Specular Hematite

Hematite (Fe2O3)

Fossilized Bone

Vertebrate Fossil Fragment (Calcium Phosphate / Hydroxyapatite)

Sedimentary Rock Fragments

Clastic Sedimentary Rock

Vesicular basalt (possibly slag-contaminated)

Basalt; chiefly plagioclase and pyroxene, with possible olivine and secondary minerals

White quartz pebble

Quartz (silicon dioxide, SiO₂)

Orange chert (likely jasper)

Microcrystalline quartz (SiO₂), iron-oxide stained; jasper is an opaque variety of chert

Druzy Quartz (on Geode Fragment)

Silicon Dioxide (SiO2)

Small rough rock fragment, likely iron-rich sedimentary rock or weathered soil-cemented material

Indeterminate from the photograph; possibly ferruginous sandstone or ironstone

Gneiss (Green Gneiss)

Gneiss (High-grade Regional Metamorphic Rock)

Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Pebble

Lithic fragment / Weathered rock fragment

Small rounded mineral/rock fragment

Indeterminate; possibly quartz-rich stone or feldspar

Small rough mineral/rock fragment

Indeterminate; possibly quartz-bearing rock or weathered feldspar

Small rounded stone or mineral fragment

Indeterminate; likely a common quartz- or feldspar-bearing silicate fragment

Likely weathered granite or granitic gneiss

Granite: quartz + feldspar + mica; possibly gneiss if foliation is present

Fossil oyster shell

Fossilized bivalve, likely Ostrea or Crassostrea; calcite (CaCO₃) shell

Unidentified dark-gray rock fragment

Undetermined; the photo is insufficient for reliable mineral or rock identification

Small pale blue-gray rock fragment

Unidentified fine-grained silicate rock; image insufficient for a reliable species-level identification

Weathered quartz-rich rock, likely granite or quartzite

Indeterminate; probable quartz–feldspar aggregate, possibly granitic gneiss

Green Fluorite

Calcium Fluoride (CaF2)