Man Made Object (Coin)

Quartzite Pebble (River Rock)

Quartzite (primarily SiO2)

Chert (Holey Stone)

Microcrystalline Quartz (SiO2)

Granitic Gneiss

Gneiss (High-grade Metamorphic Rock)

Quartz (Variety: Citrine or Tumbled Chalcedony)

Silicon Dioxide (SiO2)

Grooved Maun Ball (Maul/Hammerstone-like Concretion)

Calcareous/Ferruginous Concretion in Sandstone Matrix

Ammonite Fossil

Ammonoidea (subclass)

Ammonite Fossil (Polished Section)

Ammonoidea (typically mineralized with Calcite CaCO3)

Sandstone

Arenite (general term for sandstone)

Milky Quartz Pebble (Iron-stained)

Silicon Dioxide (SiO2)

Petrified Wood

Silicified Wood (SiO2)

Ferruginous Quartz (Iron-stained Quartz)

Quartz with Iron Oxide inclusions (SiO2 with Fe2O3)

Citrine Quartz

Silicon Dioxide (SiO2) with iron impurities

Chert / Flint

Cryptocrystalline Quartz (SiO2)

Jasper (Red Jasper with Quartz veins)

Jasper (Silicon Dioxide, SiO2)

Chert (often called Flint when dark)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Shale

Fissile mudrock (composed of clay-sized particles and detrital grains)

Sandstone

Arenite (primarily Quartz, SiO2)

Chert (Nodule)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Diabase (also known as Dolerite)

Diabase / Microgabbro

Green Fluorite

Calcium Fluoride (CaF2)

Obsidian

Volcanic glass (SiO2 - Silicon Dioxide with impurities)

Amber

Succinite (Fossilized Tree Resin)

Emerald

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

Quartz (Clear / Rock Crystal)

Silicon Dioxide (SiO2)

Hypersthene (or Enstatite/Ferrosilite)

Orthopyroxene series (Mg,Fe)SiO3 - specifically, historically hypersthene (intermediate member) now referred to as Enstatite (Mg-rich) or Ferrosilite (Fe-rich)

Milky Quartz

Silicon Dioxide (SiO2)

Limonite (Iron Ore)

Limonite (FeO(OH)·nH2O)

Serpentinite

Serpentinite ((Mg,Fe,Ni,Al)3Si2O5(OH)4)

Peridotite (Olivine/Peridot)

Peridotite: (Mg,Fe)2SiO4 (Olivine-rich ultramafic rock)

Pink Granite

Phaneritic Felsic Intrusive Igneous Rock

Alexandrite in Matrix

Chrysoberyl (BeAl2O4 with Chromium impurities)

Chert (and its variety Flint)

Silicon Dioxide (SiO2) - Microcrystalline or cryptocrystalline Quartz

Chert (variations include Flint or Jasper)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Prehnite

Prehnite (Ca2Al2Si3O10(OH)2)

Quartzite

Quartzite (primarily SiO2)

Banded Iron Formation (BIF) / Tiger Iron

Ferruginous Chert (primarily Quartz [SiO2] and Hematite/Magnetite [Fe2O3/Fe3O4])

Red Quartzite Cobble

Quartzite (primarily SiO2)

Quartz (River Pebble)

Silicon Dioxide (SiO2)

Amethyst

Amethyst (Silicon Dioxide, SiO2)

Hematite (Iron Ore)

Hematite (Fe2O3)

Granite with Epidote

Granite, containing quartz, feldspar, and epidote

Agate Nodule / Weathered Chert

SiO2 (Silicon Dioxide - Microcrystalline Quartz)