Sedimentary Or Igneous Fragment

Fossil-bearing limestone (possible shell fossil)

Fossiliferous limestone, composed mainly of calcite (CaCO₃)

Fossiliferous Limestone (Hash)

Bioclastic Grainstone / Calcarenite

Conglomerate

Conglomerate

Chalky limestone fragment

Calcite-rich limestone; predominantly calcium carbonate (CaCO₃)

Iron-stained quartz or chert fragment

Quartz (SiO₂), possibly microcrystalline quartz/chert with limonite staining

Small brown rock fragment

Undetermined; possibly weathered iron-stained quartzite or chert

Banded Agate (Geode Fragment)

Silicon Dioxide (SiO2) - Variety Agate

Geode Nodule Fragment

Quartz / Chalcedony Nodule

Weathered limestone fragment

Calcite-rich limestone (CaCO₃), possibly fossiliferous or brecciated

Conglomeratic breccia (possibly polymictic volcanic breccia)

Polymictic breccia; clasts in a fine-grained volcanic or sedimentary matrix

Breccia

Breccia (Clastic sedimentary rock)

Clear quartz crystal fragment

Quartz, silicon dioxide (SiO₂)

Crescent Pebble

Weathered Quartzite or Sandstone Fragment

River Pebble

Water-worn lithic fragment

River Stone

Water-worn lithic fragment

Generic Rock / River Pebble

Lithic fragment / Quartzite pebble

Red Painted Rock

Artificial Coated Lithic Fragment

Fossilized Shark Tooth (Partial)

Elasmobranchii (fossil tooth fragment)

Conglomerate

Conglomerate (Sedimentary rock)

Mixed collection of common river stones

Varied lithologies, visibly including quartz-rich rock, dark mafic rock, sandstone, and purple quartz-bearing material

Chalcedony Geode Fragment

Cryptocrystalline Quartz (SiO2)

Likely dark mineral or rock fragment

Indeterminate from image; possibly a dark silicate mineral such as hornblende, biotite, or basalt

Quartz-rich pebble, likely milky quartz

Quartz (silicon dioxide, SiO₂), possibly with iron-oxide or feldspar impurities

Fossiliferous Rock (Invertebrate Fossil in Matrix)

Fossiliferous limestone or shaly matrix containing skeletal fossil remains

Granite (with Quartz fragment)

Intrusive Felsic Igneous Rock

Quartz in Matrix (possibly with Biotite or Hornblende)

Quartz (Silicon Dioxide, SiO2) in Granitic Matrix

Weathered granite (probable)

Granite; quartz–feldspar–mica plutonic rock

Granite-like rock fragment

Likely leucocratic granite or granitic pegmatite; exact identification requires a fresh surface and mineral testing.

Weathered granite or granitic gneiss fragment

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

Weathered quartz-rich rock, possibly quartzite or granite fragment

Uncertain; likely quartz–feldspar aggregate, possibly altered granite or quartzite

Unidentified weathered rock fragment

Indeterminate; possibly vesicular basalt or weathered volcanic rock

Porphyritic Igneous Rock / Basalt or Andesite Xenolith in Granite or Quartzite

Silicate rock with contrasting xenolith/inclusion

Weathered limestone or calcareous sandstone

Calcite-rich carbonate rock, chiefly calcium carbonate (CaCO₃), possibly fossiliferous limestone

Likely quartz-rich stone or pale feldspar fragment

Indeterminate; possibly quartz (SiO₂) or feldspar (KAlSi₃O₈–NaAlSi₃O₈)

Basalt

Basalt (Extrusive Igneous Rock)

Milky quartz fragment

Quartz (silicon dioxide, SiO₂)

Greenish translucent mineral fragment

Indeterminate; possibly serpentine, epidote, or green glassy feldspar

Rounded quartz-rich river pebble

Likely quartz arenite or chert-derived sandstone; identification is limited from the photograph

Chert

Microcrystalline Quartz (SiO2)

Brecciated Chert

Brecciated Chert (Microcrystalline Quartz, SiO2)

Milky quartz (rough quartz fragment)

Quartz, silicon dioxide (SiO₂)

Possible flint (chert) fragment

Microcrystalline quartz (SiO₂), commonly called flint when dark and nodular