Rock

Granite (weathered/river-tumbled)

Granite (Plutonic Igneous Rock)

Vesicular Basalt

Vesicular Basalt (Aphanitic Mafic Igneous Rock)

Red Sandstone

Clastic sedimentary rock (primarily Quartz with Hematite)

Sandstone

Arenite (SiO2 based)

Sandstone (Calcareous Sandstone)

Calcareous Sandstone (primarily SiO2 with CaCO3 cement)

Gneiss

Gneiss

Pyrite in Slate or Shale

Iron Sulfide (FeS2) in Argillaceous Matrix

Serpentinite (Serpentine Rock)

Primarily composed of serpentine group minerals, such as antigorite, chrysotile, and lizardite. Chemical formula for serpentine minerals is (Mg,Fe)3Si2O5(OH)4.

Basalt

Mafic extrusive igneous rock

Basalt

Basalt

Sandstone

Arenite (specifically sublithic or quartz arenite)

Sandstone (with potential iron-oxide weathering)

Arenite (SiO2 based)

Limestone

Limestone (CaCO3)

River Pebble / Chert Pebble

Microcrystalline Quartz (SiO2)

Limestone

Calcium Carbonate (CaCO3)

Red Sandstone

Arenite (Ferruginous Sandstone)

Limestone

Calcium Carbonate (CaCO3)

Limestone

Limestone (Calcium Carbonate - CaCO3)

Limestone

Calcium Carbonate (CaCO3)

Concrete fragment with Aggregate

Anthropogenic Concrete with Calcarious and Siliceous Aggregate

Limestone

Sedimentary Limestone (Calcium Carbonate, CaCO3)

Ferruginous Sandstone

Arenite with Hematite/Goethite cement

Sandstone (Ferruginous)

Arenite (primarily SiO2 with Iron Oxide staining)

Limestone

Calcium Carbonate (CaCO3)

Quartzite with Iron Inclusions

Metamorphic Quartzite (SiO2 with Fe2O3 trace impurities)

Mudstone

Lutylite (group of fine-grained sedimentary rocks)

Eclogite

Eclogite (Pyrope garnet and Omphacite pyroxene)

Sandstone (likely Quartzose type)

Clastic sedimentary rock (primarily SiO2)

Red Sandstone

Arenite (with Iron Oxide / Hematite cementation)

Limestone

Calcium Carbonate (CaCO3)

Sandstone (likely Quartzose Sandstone)

Arenite (SiO2 predominantly)

Limestone (specifically Iron-stained or Argillaceous Limestone)

Calcium Carbonate (CaCO3) with Iron Oxide (Fe2O3) impurities

Ocherous Sandstone (Ferruginous Sandstone)

Ferruginous Arenite (SiO2 with Fe2O3)

Quartz Geode

Silicon Dioxide (SiO2) within a geode

Sandstone

Arenite (primarily SiO2 - Silicon Dioxide)

Stream Pebble (Basalt/Greywacke)

Mafic Igneous Rock (Fine-grained)

Limestone

Calcium Carbonate (CaCO3)

Ferruginous Sandstone (with possible Epidote/Chlorite coloring)

Sandstone (SiO2 dominated with Fe2O3 staining)

Ferruginous Sandstone

Arenite with Iron-Oxide cement (primarily Fe2O3 • nH2O)

Granite Water-Worn Pebble

Granite (composed primarily of Quartz, Feldspar, and Mica)

Biotite (Black Mica)

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

Sandstone

Sedimentary Rock (Quartz arenite)