Not A Rock

Limestone

Calcium Carbonate (CaCO3)

Fossilized Brachiopod/Bivalve in Limestone

Brachiopoda or Bivalvia fossil in Calcite/Limestone (CaCO3)

Porphyritic Basalt (Chinese Writing Stone)

Porphyritic Basalt or Porphyritic Andesite

Pink Granite

Phaneritic Felsic Intrusive Igneous Rock

Basalt

Basalt (extrusive igneous rock)

Arkosic Sandstone

Arkose (Clastic Sedimentary Rock)

Sandstone (Ferruginous)

Arenite (Fe-rich)

Limestone

Limestone (Calcium Carbonate - CaCO3)

Sandstone (lithic/greywacke variety)

Arenite (composed primarily of SiO2 with various lithic fragments)

Eclogite

Eclogite (comprising Omphacite and Garnet)

Limestone

Calcium Carbonate (CaCO3)

Crushed Limestone (Gravel)

Calcium Carbonate (CaCO3)

Limestone

Calcium Carbonate (CaCO3)

Limestone (with potential fossil inclusions)

Calcium Carbonate (CaCO3)

Quartzite with Iron Staining

Quartzite (primarily SiO2 with Fe2O3 staining)

Quartzite (Iron-stained)

Quartzite (SiO2 with Fe-oxides)

Granodiorite / Granite

Granodiorite (containing Quartz SiO2, Plagioclase Feldspar, and Biotite)

Limestone (Brecciated/Recrystallized)

Calcium Carbonate (CaCO3)

Limestone

Calcium Carbonate (CaCO3)

Limestone (Grey and White specimens)

Calcium Carbonate (CaCO3)

Granite Cobble

Phaneritic Felsic Igneous Rock

Sandstone (with Iron Staining)

Clastic sedimentary rock (primarily SiO2)

Sandstone (Water-worn Pebble)

Clastic sedimentary rock (primarily SiO2)

Granite

Granite (phaneritic felsic intrusive rock)

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

Sandstone (Pebble/Cobble)

Arenite (primarily SiO2)

Amethyst (Geode/Druzy)

Silicon Dioxide (SiO2) with iron impurities

River Pebbles (Tumbled Quartz and Basalt)

Silicon Dioxide (SiO2) for white quartz; Mafic Volcanic Rock for basalt

Ferruginous Sandstone

Clastic sedimentary rock (primarily SiO2 with Fe2O3 cement)

Quartzite (specifically a river-worn pebble)

Quartzite (primarily SiO2)

Sandstone (Ferruginous)

Arenite (with high iron oxide content)

Quartzite with Quartz Vein

Metamorphosed sandstone (SiO2)

Sandstone Pebble

Arenite (primarily SiO2)

Sandstone (Calcareous or Ferruginous)

Clastic sedimentary rock (SiO2 with CaCO3 or Fe2O3 cement)

Garnet Schist

Garnet-bearing Mica Schist (variety of compositions, often Al2SiO5 with X3Y2(SiO4)3)

Ferruginous Sandstone (Ironstone)

Clastic sedimentary rock (SiO2 with Fe2O3/FeO(OH) cement)

Sandstone (Ferruginous)

Arenite (composed primarily of SiO2 with Fe2O3 cement)

Limestone

Calcium Carbonate (CaCO3)

River/Stream Pebble

Clast / Detrital Grain / Rounded Sedimentary Particle (Compositionally variable, commonly Quartz, Feldspar, Chert, or other resistant rock fragments)

Sandstone (Ferruginous)

Arenite with Iron-Oxide Cement

Sandstone (with carbonaceous plant fragments)

Arenite (composed primarily of SiO2)

Milky Quartz

Silicon Dioxide (SiO2)