Not A Geological Specimen

Pyrite (Fool's Gold)

Iron Sulfide (FeS2)

Chert (specifically Red Chert or Jasper)

Microcrystalline Quartz (SiO2)

Glauconite

(K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2

Manganese Oxide Crust on Limestone

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

Yellow Citrine Quartz

Silicon Dioxide (SiO₂)

Celestite (Celestine)

Strontium sulfate (SrSO4)

Sandstone

Arenite (Siliclastic Sedimentary Rock)

River Pebbles (Tumbled Quartz and Basalt)

Silicon Dioxide (SiO2) for white quartz; Mafic Volcanic Rock for basalt

Horn Coral Fossil

Rugosa (Order Rugosa)

Citrine Quartz

Silicon Dioxide (SiO2)

Amygdaloidal Basalt

Basalt with secondary mineral infilling

Petrified Wood

Silicified wood (primarily SiO2)

Orthoclase Feldspar (Sunstone variety)

KAlSi3O8 (Potassium Aluminum Silicate)

Basalt with Calcite Veining

Aphanitic Mafic Igneous Rock (Basalt) with CaCO3

Porphyritic Basalt (Leopard Rock)

Porphyritic Mafic Volcanic Rock

Michigan Float Copper

Native Copper (Cu)

Moqui Marble (Shaman Stone)

Iron Oxide Concretion (Hematite/Goethite-encased Sandstone)

Fluorite

Calcium Fluoride (CaF2)

Feldspar Rich Granite with Limonite Staining

K-Feldspar Granite (KAlSi3O8)

Graphite-veined Quartzite

Meta-sedimentary Quartzite with Carbonaceous/Graphitic Inclusions (SiO2 + C)

Chert (Iron-stained)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Aragonite (Botryoidal/Coralloidal variety)

Aragonite (CaCO3)

Malachite and Azurite on Gossan (Ironstone Matrix)

Cu2CO3(OH)2 (Malachite) on FeO(OH)·nH2O (Limonite/Gossan)

Sodalite

Sodalite (Na8(Al6Si6O24)Cl2)

Petrified Dinosaur Bone (Gembone)

Agatized Dinosaur Bone

Granite Cobble

Felsic intrusive igneous rock

Note: Image shows a biological specimen (Rat), not a rock. Representative geological equivalent: Galena (due to lead-grey colors in fur).

Galena (PbS)

Quartzite Pebble

Quartzite (mostly SiO2)

Quartz (Iron-stained)

Silicon Dioxide (SiO2)

Chert Pebble

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Quartz (Flesh-colored or Rose Quartz variety)

Silicon Dioxide (SiO2)

Basalt (with possible weathering or secondary mineral crust)

Basalt (Aphanitic Mafic Igneous Rock)

Yellow Quartzite (River Stone)

Quartzite (composed primarily of Quartz: SiO2)

Dyed Pink Agate Slice

Cryptocrystalline variety of Quartz (SiO2)

Basalt (River Pebble)

Basalt

Limestone (specifically Travertine or Tufa)

Calcium Carbonate (CaCO3)

Quartz (Milk Quartz Cobble)

Silicon Dioxide (SiO2)

Quartz Pebble

Silicon Dioxide (SiO2)

Quartz Pebble

Silicon Dioxide (SiO2)

Granite

Granite (Felsic Plutonic Rock)

Gneiss (with Quartzite and Biotite)

Gneiss containing SiO2 (Quartz), K(Mg,Fe)3AlSi3O10(OH)2 (Biotite), and (K,Na,Ca)AlSi3O8 (Feldspar)

Quartzite Pebble

Quartzite (SiO2)