Mineral Like Biological Tissue

Obsidian

Extrusive igneous volcanic glass (rich in SiO2)

Prehnite

Prehnite - Ca2Al(AlSi3O10)(OH)2

Hematite (Iron Ore)

Hematite (Fe2O3)

Gemstone Sand (Mineral Assortment)

Mixed Mineral Concentrates (Commonly including Quartz SiO2, Garnet X3Y2(SiO4)3, and Tourmaline (Na,Ca)(Li,Mg,Al)3(Al,Fe,Mn)6(BO3)3(Si6O18)(OH,F)4)

Agate (specifically, multi-colored or pastel-dyed agate)

Silicon dioxide (SiO2) - specifically, a cryptocrystalline variety of quartz known as Chalcedony, with banding classified as Agate. (If it were Fluorite, the chemical formula would be Calcium Fluoride - CaF2).

Mica Schist

Schist (Crystalline metamorphic rock)

Clear Quartz

Silicon Dioxide (SiO2)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Sandstone

Sandstone (Sedimentary rock composed of silicate grains)

Sandstone (specifically Cross-bedded Sandstone)

Arenite (composed primarily of SiO2)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Geode (unopened)

SiO2 - Chert-shelled concretion (mostly Quartz)

Peacock Ore

Bornite (Cu5FeS4) or iridescent Chalcopyrite (CuFeS2)

Dendritic Agate

Silicon Dioxide with Manganese/Iron oxide inclusions (SiO2)

Granite Gneiss with Garnet

Garnetiferous Gneiss

Chert (varieties include Flint or Jasper)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Agate

Silicon dioxide (SiO2)

Moss Agate

Silicon Dioxide (SiO2) with Chlorite/Oxide inclusions

Geode (Unbroken)

Silicon Dioxide (SiO2) usually as Microcrystalline Quartz or Chalcedony

Fluorite (Rainbow, Purple-Blue Tumbled)

Calcium Fluoride (CaF2)

Quartz (Milky or Iron-Stained)

Silicon Dioxide (SiO2)

Bronzite

Enstatite (var. Bronzite), (Mg,Fe)SiO3

Blue Quartzite (River Pebble)

Quartzite (primarily SiO2 with Dumortierite or Crocidolite inclusions)

Quartz / Quartz Geode fragment

Silicon Dioxide (SiO2)

Magnetite (Lodestone variety)

Magnetite (Iron(II,III) oxide, Fe3O4)

Limonite (Iron Ore)

Hydrous ferric oxides (FeO(OH)·nH2O)

Rhodonite

Manganese Silicate (Mn,Fe,Mg,Ca)SiO3

Specular Hematite

Specularite (Iron Oxide, Fe2O3)

Obsidian

Volcanic Glass (SiO2 rich)

Quartz (Chert/Chalcedony Variety)

Silicon Dioxide (SiO2)

Schist

Mica Schist (Medium-grade metamorphic rock)

Sandstone (likely Ferruginous)

Sandstone (SiO2 with iron oxides)

Tiger's Eye (Tumbled Blue/Black-Golden variety)

Pseudomorph of Quartz after Crocidolite (SiO2 with Iron inclusions)

Goethite

Goethite (α-FeO(OH))

Quartz

Silicon Dioxide (SiO₂)

Sandstone (Ferruginous)

Arenite (with Iron Oxide)

Glauconite

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

Amethyst

Crystalline Quartz (SiO2) with iron impurities

Obsidian

Volcanic Glass (SiO2)

Orthoclase Feldspar

Orthoclase (KAlSi3O8)

Gneiss (specifically a weathered Amphibolite or Garnet Gneiss)

Gneiss (complex silicate composition)

Arfvedsonite (often mistakenly sold as Astrophyllite)

Arfvedsonite [Na3(Fe2+)4Fe3+Si8O22(OH)2]