Crystal

Clear Quartz Crystal

Quartz (Silicon Dioxide, SiO2)

Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Quartz Crystal Fragment

Silicon Dioxide (SiO2)

Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Quartz (Crystal Cluster)

Silicon Dioxide (SiO2)

Quartz Crystal (specifically a Double-Terminated variety)

Silicon Dioxide (SiO2) - Low Quartz

Clear Quartz Crystal

Silicon Dioxide (SiO2)

Rough Quartz Crystal in Matrix

Silicon Dioxide (SiO2)

Clear Quartz Crystal

Silicon Dioxide (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Quartz (Crystal Fragment)

Silicon Dioxide (SiO2)

Amethyst (Rough Crystal)

Silicon Dioxide (SiO2 with ferric iron impurities)

Quartz Crystal Cluster

Silicon Dioxide (SiO2)

Quartz Crystal Point

Silicon Dioxide (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Smoky Quartz and Feldspar Pegmatite

Granitic Pegmatite (chiefly SiO2 and KAlSi3O8)

Quartz Crystal with Inclusions

Silicon Dioxide (SiO2)

Druzy Quartz Geode (likely Smokey Quartz variety)

Silicon Dioxide (SiO2) - specifically a geode formation lined with druzy quartz crystals, with a likely brownish hue indicating smokey quartz.

Quartz Crystal Cluster

Quartz (Silicon Dioxide, SiO2)

Clear Quartz

Silicon Dioxide (SiO2)

Granite Pegmatite

Phaneritic Plutonic Igneous Rock

Diamond (Uncut Crystal)

Carbon (C)

Chlorite Phantom Quartz

Silicon Dioxide (SiO2) with Chlorite group inclusions [(Mg,Fe)3(Si,Al)4O10(OH)2·(Mg,Fe)3(OH)6]

Strawberry Quartz

Quartz with Hematite inclusions (SiO2 + Fe2O3)

Prasiolite and Quartz Crystal Cluster

Quartz (SiO2); Prasiolite is a variety of Quartz

Milky Quartz

Silicon Dioxide (SiO2)

Lapis Lazuli (Lazurite crystals on Marble)

Lazurite / (Na,Ca)8[(S,Cl,SO4,OH)2|(AlSiO4)6]

Rutilated Quartz

Silicon Dioxide (SiO2) with Titanium Dioxide (TiO2) inclusions

Clear Quartz / Rock Crystal

Silicon Dioxide (SiO2)

Clear Quartz (or Rock Crystal)

Quartz (SiO₂)

Clear Quartz

Silicon Dioxide (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Amethyst (Polished/Carved Crystal)

Silicon Dioxide (SiO2) with trace Iron (Fe)

Man-made Crystal (Lead Glass)

Lead oxide-doped Silica Glass (approx. SiO2 + PbO)

Obsidian and Phantom Quartz

Volcanic Glass (SiO2 + MgO + Fe3O4) and Crystalline Quartz (SiO2)

Kyanite (Blue or Blue-Grey)

Kyanite (Al2SiO5)

Quartz Druze (on Matrix)

Silicon Dioxide (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Obsidian

Obsidian (Volcanic Glass)

Calcite (or Alabaster, if truly carved)

Calcium Carbonate (CaCO3)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)