Man Made Glass (Not A Natural Rock Or Mineral)

Black Diamond / Black Sapphire

Carbon (C) or Corundum (Al2O3)

Pumice

Pumicite (fine-grained pumice), Scoria (similar origin but denser and darker, usually basaltic)

Obsidian

Obsidian (volcanic glass), amorphous SiO2 + impurities

Chert / Flint Nodule

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Clear Quartz (Rock Crystal)

Quartz (Silicon Dioxide, SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Hematite

Iron (III) Oxide (Fe2O3)

Chert (Nodular Chert)

Silicon Dioxide (SiO2)

Basalt with Scoria

Amygdaloidal Basalt / Vesicular Basalt

Fluorite-Gedrite in Quartz (Schist)

Fluorite (CaF2) with Gedrite in Quartz/Feldspar Matrix

Pumice

Pumicite

Rose Quartz

Silicon Dioxide (SiO2)

Yellow Calcite

Calcium Carbonate (CaCO3)

Chrysoprase

Chalcedony (cryptocrystalline SiO2 variety)

Obsidian (Arrowhead Lithic Tool)

Obsidian (Amorphous Volcanic Glass / SiO2 + inclusions)

Citrine Quartz Crystal Cluster

Silicon Dioxide (SiO2) with iron impurities

Manganese Oxide Crust on Limestone

Manganese Oxides (e.g., Pyrolusite MnO2 or Romanechite) on CaCO3

Yellow Chert

Sedimentary cryptocrystalline quartz (SiO2)

Red Jasper

Silicon Dioxide (SiO2) with Hematite inclusions

Chert (often called Flint or Jasper)

Silicon Dioxide (SiO2)

Emerald

Beryl (Be3Al2(SiO3)6) with Chromium and/or Vanadium impurities

Nephrite Jade

Nephrite (Ca2(Mg, Fe)5Si8O22(OH)2)

Herkimer Diamond

Quartz (Silicon Dioxide) - SiO2

Jasper and Quartz River Cobble

Silicon Dioxide (SiO2) with Hematite inclusions

Quartzite

Quartzite (SiO2)

Pearl

Calcium Carbonate (CaCO3) - mainly Aragonite and Calcite

Diamond

Native Carbon (C)

Pink Tourmaline in Quartz Matrix

Elbaite (Na(Li,Al)3Al6(Si6O18)(BO3)3(OH)4) in Quartz (SiO2)

Diamond

Carbon (C)

Blue Sapphire

Corundum (Al2O3 with trace Titanium/Iron)

Blue Sapphire

Corundum (Al2O3)

Scoria (Lava Rock)

Vesicular Basalt / Scoria

Banded Sandstone (Quartzite-rich)

Clastic Sedimentary Rock (SiO2 with Iron Oxide impurities)

Dalmatian Jasper / Dalmatian Stone

Peralkaline Rock (Silicon Dioxide with Amphibole inclusions)

Serpentine

Antigorite, Lizardite, or Chrysotile (Mg, Fe)3Si2O5(OH)4

Note: Item is not a geological specimen

Homo sapiens (Dermal Appendage: Pilus)

Dyed Alum or Dyed Quartz (Ornamental Crystal)

Silicon Dioxide (SiO2) or Potassium Alum [KAl(SO4)2·12H2O]

Silicon Carbide (Carborundum)

Moissanite (SiC), though mostly synthetic

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Limestone

Calcium Carbonate (CaCO3)