Anthropogenic (Man Made Material)

Banded Ironstone / Jasper Siltstone

Siltstone with Iron Oxide Hydrates (SiO2 with Fe2O3/FeO(OH))

Granite

Granite (Plutonic Igneous Rock)

Quartz with Mafic/Chlorite Veins

Silicon Dioxide (SiO2) with Chlorite/Epidote cross-veining

Sandstone

Sandstone (SiO2 rich)

Sandstone / Limestone

Sedimentary Rock (Quartz Sandstone or Calcareous Grainstone)

Amygdaloidal Basalt

Amygdaloidal Basalt (containing quartz/agate or zeolite fill)

Quartzite with Quartz Veins

Metamorphic Quartz-rich Rock (SiO2)

Sandstone

Arenite (SiO2 principal component)

Sandstone

Arenite (SiO2 based)

Yellow Quartzite Pebble

Quartzite (primarily SiO2)

Sandstone (Calcareous/Lithic)

Sedimentary Rock (Clastic Sandstone with Calcium Carbonate cement)

Quartzite (River Pebble)

Metamorphosed Quartz Sandstone (SiO2)

Quartzite Cobble

Quartzite (primarily SiO2)

Limestone (River Stone)

Calcium Carbonate (CaCO3)

Quartz (Common or Milky Quartz) with Iron Staining

Silicon Dioxide (SiO2)

Yellow Quartzite (Citrine-colored Quartz)

Silicon Dioxide (SiO2) with iron oxide inclusions

Sandstone

Clastic sedimentary rock (Quartz arenite)

Jasper Conglomerate

Polymictic Conglomerate (Quartz and Jasper clasts in a quartz-rich matrix)

Yellow Jasper

SiO2 (Microcrystalline Quartz)

Unakite

Altered Granite (Epidotized Granite)

Milky Quartz

Silicon Dioxide (SiO2)

Quartz Pebble

Silicon Dioxide (SiO2)

Green Greenstone / Celadonite-bearing Metamorphic Rock

Greenschist / Celadonite / Serpentinitic pebble

Unakite

Metamorphosed Granite (Epidotized Feldspar and Quartz)

Agate (Carnelian / Fire Agate nodule)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Granite / Diorite (Granitoid)

Granitoid rock (composed mainly of Quartz, Feldspar, and Amphibole/Biotite)

Basalt (Beach Pebble) / Black Chert

Basalt / Microcrystalline Quartz (SiO2)

Carnelian / Chalcedony

Silicon Dioxide (SiO2)

Banded Serpentinite (Beach Pebble)

Serpentine-group silicate rock ((Mg,Fe,Ni,Al,Zn,Mn)3(Si,Fe,Al)2O5(OH)4)

Rhodochrosite

Manganese Carbonate (MnCO3)

Quartz-veined Greywacke

Silicon dioxide (SiO2) in Lithic Sandstone

Granite Pebble

Granite (Phaneritic intrusive igneous rock)

Quartzite

Quartzite (SiO2)

Limestone

Calcium Carbonate (CaCO3)

Sandstone Pebbles

Arenite (primarily SiO2 with mineral cement)

Quartzite

Quartzite (primarily SiO2)

Chert Conglomerate (Potomac Puddle Stone)

Sedimentary Conglomerate with Iron-Oxide matrix

Sandstone

Arenite (composed primarily of SiO2)

Limestone (likely weathered)

Limestone (Mainly Calcium Carbonate, CaCO3)

Orbicular Jasper (Ocean Jasper)

Silica-rich Microcrystalline Quartz (SiO2) with various inclusions

Quartzite

Metamorphosed Quartz Sandstone (SiO2)

Coquina

Biogenic Limestone (Calcium Carbonate, CaCO3)