Igneous Rock

Quartz (likely)

Quartz (SiO2 - Silicon Dioxide)

Biotite (Black Mica)

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

Granite and Igneous Mix

Phaneritic Felsic to Mafic Intrusive Rocks

Banded Calcite (often sold as 'Travertine' or 'Mexican Onyx')

Calcium Carbonate (CaCO3)

Limestone

Calcium Carbonate (CaCO3)

Quartz Vein on Matrix

Silicon Dioxide (SiO2)

Limestone

Calcium Carbonate (CaCO3)

Sandstone (Quartzose)

Arenite (primarily SiO2)

Schist

Mica Schist (primarily consisting of muscovite KAl2(AlSi3O10)(OH)2 or biotite K(Mg,Fe)3(AlSi3O10)(OH)2)

Sandstone

Arenite (SiO2 based)

Milky Quartz with Iron Staining

Silicon Dioxide (SiO2)

Milky Quartz

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2) in Host Rock

Rose Quartz

Silicon Dioxide (SiO2) with trace amounts of titanium, iron, or manganese

Ammonite Fossil in Limestone Matrix

Ammonoidea (subclass) in Calcium Carbonate (CaCO3)

Not a rock, mineral, or geological specimen

Milky Quartz

Silicon Dioxide (SiO2)

Amethyst (Chevron Amethyst)

Amethystine Quartz (SiO2)

Pyrite in Shale

Iron Sulfide (FeS2) in Sedimentary Matrix

Petrified Wood

Silicified Wood (SiO2)

Chert (variations include Flint or Jasper)

Cryptocrystalline Quartz (SiO2)

Sandstone (Ferruginous Concretion)

Ferruginous Sandstone Concretion / SiO2 with Fe2O3 cement

Schist

Schist (Crystalline metamorphic rock)

Quartz Vein in Pelite (Metamorphic Rock)

Hydrothermal Quartz Veining in Metasedimentary Rock (SiO2)

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Copper-bearing Quartz (likely Chrysocolla or Malachite staining)

Cuprite, Chrysocolla (Cu2-xAlx(H2-xSi2O5)(OH)4·nH2O) or Malachite staining on Quartz/Host Rock

Jasper

Silicon dioxide (SiO2)

Chert (specifically Gray Chert)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Coquina

Bioclastic Limestone

Quartz / Common Opal

Silicon Dioxide (SiO2)

Chert / Flint

Chert (Microcrystalline Quartz, SiO2)

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Wishing Stone (Gneiss or Basalt with Quartz Vein)

Gneiss or Metabasalt (with a Quartz or Calcite intrusion)

Chalcedony

Cryptocrystalline Quartz (SiO2)

White Quartz (Tumbled)

Silicon Dioxide (SiO2)

Unakite

Epidotized Granite

Exposed Aggregate Concrete (Pea Gravel)

Concrete with Siliceous Alluvial Gravels

Unakite

Unakite (Epidotized Granite)

Unakite

Epidotized Granite

Unakite

Unakite (Epidotized Granite)

Unakite

Epidotized Granite (SiO2 with Ca2(Al, Fe)3(SiO4)3(OH))