Mineraloid (Human Made Geological Specimen)

Chert (Brown Variety)

Microcrystalline quartz (SiO2)

Aragonite Star Cluster

Aragonite (Sputnik habit) - CaesarCO3

Amethyst

SiO2 (Silicon Dioxide with iron impurities)

Diamond Drill Core (Greenschist and Quartzite)

Chlorite Schist / Meta-quartzite (Metamorphic Rock Core Sample)

Conglomerate

Conglomerate (SiO2 dominant in clasts)

Milky Quartz with Iron Staining

Quartz (Silicon Dioxide, SiO2)

Quartz (Smoky/Milky variety)

Silicon Dioxide (SiO2)

Chert (with Quartz Veining)

Chert (formula: SiO2)

Red Siltstone

Siltstone (primarily quartz and feldspar sized 0.0039 to 0.0625 mm)

Cupronickel (on a 1981 Mexico 20 Pesos coin)

Copper-Nickel Alloy (Cu75Ni25)

Travertine (Calcareous Tufa)

Calcium Carbonate (CaCO3)

Red Sandstone

Arenite (predominantly SiO2 with Fe2O3)

Garnet in Matrix (likely Almandine in Quartz/Mica Schist)

Almandine Garnet (Fe3Al2(SiO4)3) in Quartz-Feldspar host rock

Pink Granite

Granite (rich in Potassium Feldspar/Orthoclase)

igneous

Epidote with Unakite characteristics

{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)

Ferruginous Quartz

Silicon Dioxide (SiO2) with Iron Oxide (Fe2O3) inclusions

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Rose Quartz

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

Amethyst

Amethyst (Silicon Dioxide, SiO2)

Amethyst

SiO2 (Silicon Dioxide with Iron impurities)

Smoky Quartz

Smoky Quartz (Silicon Dioxide - SiO2)

Satin Spar (Selenite)

Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O

Clear Quartz

Silicon Dioxide (SiO2) / Rock Crystal

Granite

Phaneritic Plutonic Felsic Rock (SiO2, KAlSi3O8, NaAlSi3O8, CaAl2Si2O8)

igneous

Freshwater Pearl

Aragonite / Biogenic Calcium Carbonate (CaCO3)

Ruby (set in a gold pendant)

Ruby (Variety of Corundum, Al2O3)

Sandstone with Foliose Lichen

Arenite (Rock matrix) with Xanthoparmelia or Flavoparmelia (Lichen genus)

Quartzite

Quartzite (primarily SiO2)

Sandstone

Arenite (SiO2 based with various mineral cements)

Red Garnet

Pyrope or Almandine (Silicate group, X3Y2(SiO4)3)

Mineral

Granite

Intrusive Igneous Rock (composed primarily of Quartz: SiO2, Feldspar: KAlSi3O8, and Mica: KAl2(AlSi3O10)(OH)2)

igneous

Muscovite Mica

Muscovite (KAl2(AlSi3O10)(OH)2)

Sandstone

Arenite (primarily SiO2)

Blue Dyed Agate Geode

Chalcedony (cryptocrystalline Quartz), SiO2

Yellow Calcite

Calcium Carbonate (CaCO3)

Milky Quartz

Quartz (Silicon Dioxide - SiO2)

Milky Quartz

Silicon Dioxide (SiO2)

Quartz (Milky/Clear Quartz)

Silicon Dioxide (SiO2)

Rough Green Calcite

Calcite (Calcium Carbonate, CaCO3)

Clear Quartz

Silicon Dioxide (SiO2)