Mineral (Biogenic Replacement)

Pyrite with galena and sphalerite

Pyrite (FeS₂), commonly intergrown with galena (PbS) and sphalerite (ZnS)

Tiger's Eye

Pseudomorph of Quartz after Crocidolite (SiO2)

Chert (Commonly known as Flint)

Microcrystalline Quartz (SiO2)

Fossilized Coral (Petrified Coral)

Lithostrotionella (example genus) / Scleractinia

Hematite pseudomorph after a fossil or mineralized object (likely iron-oxide concretion)

Hematite, Fe₂O₃, possibly limonite/goethite-bearing

Hematite

Iron(III) oxide (Fe2O3)

Petrified wood

Silicified fossil wood; commonly quartz (SiO₂) replacing wood

Orbicular jasper (orbicular chert/jasper)

Silica-rich microcrystalline quartz (chalcedony), SiO₂, with iron-oxide and other mineral inclusions

Likely galena-bearing sulfide specimen

Galena (PbS), possibly with pyrite or other sulfides

Galena-rich sulfide specimen

Galena (lead sulfide, PbS), possibly with sphalerite or other sulfides

Tiger's Eye

Pseudomorph of Quartz after Crocidolite (SiO2 with iron inclusions)

Likely metallic mineral specimen

Probably galena (lead sulfide, PbS), though visual identification is uncertain

Likely polished dark pebble

Indeterminate; possibly basalt, black jasper, or a dark sulfide-rich stone

Sphalerite in Matrix (Polished Point)

Zinc sulfide (Zn,Fe)S

Black Jasper

Black Jasper (Silicate mineral - SiO2)

Chert with Chalcedony/Quartz Vug

Cryptocrystalline Silica (SiO2)

Amethyst

Silicon Dioxide (SiO2) with trace Iron (Fe3+)

Chert (specifically Flint or Jasper variant)

Microcrystalline Quartz (SiO2)

Ocean Jasper (Orbicular Jasper)

Spherulitic Chalcedony (SiO2)

Chert Nodule

Microcrystalline Quartz (SiO2)

Yellow Chert or Jasper

Silicon Dioxide (SiO2)

Green-blue fluorite specimen

Fluorite (calcium fluoride, CaF₂)

Chrysocolla-rich copper ore

Chrysocolla (hydrated copper aluminosilicate), likely with malachite and copper oxides

Thulite in Matrix

Pink Zoisite - Ca2Al3(SiO4)3(OH)

Yellow-brown jasper or silicified volcanic rock

Microcrystalline quartz (chalcedony), SiO₂, likely jasper

Galena

Lead(II) sulfide (PbS)

Fossilized oyster shell

Ostrea/Exogyra sp.; calcium carbonate (mostly calcite)

Polished orbicular jasper

Siliceous microcrystalline quartz (chalcedony), SiO₂, with iron-oxide and other mineral inclusions

Radiating stibnite crystals

Stibnite (antimony sulfide, Sb₂S₃)

Tumbled brown stone, likely tiger’s-eye or jasper

Quartz-rich microcrystalline silica, likely SiO₂ (possible tiger’s-eye; identification uncertain from image)

Galena

Lead(II) sulfide (PbS)

Sodalite

Na8(Al6Si6O24)Cl2 (Sodium Aluminum Silicate Chloride)

Chalcedony (Botryoidal or Tumbled)

Chalcedony (SiO₂)

Chert (Chalcedony/Agate Pebble)

Microcrystalline Quartz (SiO2)

Fossil Rugose Coral (Horn Coral)

Order Rugosa (likely Grewingkia or Heliophyllum species); Calcium Carbonate (CaCO3)

Petrified Coral (Agatized Coral)

Fossilized Anthozoa (Silicon Dioxide replacement - SiO2)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Chert (variant Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Geode / Fossilized Gastropod or Shell Cast

Silicon dioxide (Quartz) replacement / fossil mold

Chert (River Pebble)

Microcrystalline Quartz (SiO2)

Megalodon Shark Tooth Fossil

Otodus megalodon (fossilized in sedimentary matrix)

Weathered iron-rich stone, likely ironstone or hematite-bearing chert

Goethite–hematite-rich ironstone; possibly ferruginous chert (FeO(OH)/Fe₂O₃ with silica)