Mineral (Silicate Replaced Organic Material)

Jasper (Red Jasper)

Silicon Dioxide (SiO₂)

Limestone or Sandstone Cobble

Sedimentary rock (Calcium carbonate or Quartz based)

Silicified Gastropod Fossil (Agatized Fossil)

Gastropoda (Class) preserved in Chalcedony/Quartz (SiO2)

Petrified Wood

Silicified wood (primarily Silicon Dioxide - SiO2)

Dendritic jasper/chalcedony

Silica-rich microcrystalline quartz (SiO₂) with manganese-oxide dendrites

Unakite

Epidotized Granite (Fe, Ca, Al silicate + KAlSi3O8)

Chert or chalcedony nodule

Microcrystalline quartz (SiO₂), possibly weathered chert

Enrolled Trilobite Fossil

Phylum Arthropoda, Class Trilobita (likely Calymene or Flexicalymene)

Chert with Limestone Cortex

Silicon Dioxide (SiO2) with Calcium Carbonate (CaCO3)

Chert

Microcrystalline Silicon Dioxide (SiO2)

Chert (Nodule)

Silicon Dioxide (SiO2)

Petrified Wood

Silicified Wood (SiO2)

Sandstone Concretion

Sedimentary Clastic Rock (Silicate-rich)

Petrified Wood

Silicified Wood (SiO2)

Petrified Wood

Silicified Wood (SiO2)

Chert (likely brown flint)

Microcrystalline quartz, SiO₂ (chalcedonic quartz aggregate)

Kaolinite (Chalky Clay)

Kaolinite (Al2Si2O5(OH)4)

Fossilized Shark Teeth

Otodus sp. (Eocene Sand Tiger/Mackerel Shark)

Bivalve Fossil

Bivalvia (Phylum Mollusca)

Chert (and Flint)

Silicon Dioxide (SiO2)

Smelter Slag

Anthropogenic Silicate Slag

Petrified Wood

Silicified Wood (SiO2)

Tektite

Impactite (Natural Silicate Glass)

Chert (Yellow/Brown variety)

Chert (SiO2)

Petrified Wood

Silicified wood (Quartz / Chalcedonized wood, SiO2)

Fossilized Shark Tooth (Megalodon or Carcharocles fragment)

Elasmobranchii (Fossilized tooth root / crown section)

Tumbled brown jasper

Microcrystalline quartz/chalcedony (SiO₂), commonly iron-oxide stained

Biotite (Mica)

K(Mg,Fe)3AlSi3O10(OH,F)2

Biotite (Mica)

Biotite (K(Mg,Fe)3AlSi3O10(OH,F)2)

Polished ocean jasper (orbicular jasper)

Microcrystalline quartz (SiO₂) with chalcedony, iron oxides, and assorted silicate inclusions

Petrified Wood

Silicified wood (primarily SiO2)

Chert (variations include Flint or Jasper)

Silicon Dioxide (SiO2)

Chert

Microcrystalline Quartz (SiO2)

Petrified Wood

Silicified Wood (SiO2)

Fossil gastropod (snail)

Fossilized gastropod shell, likely a marine mollusk; exact genus cannot be determined from the image

Chert / Chalcedony

Silicon Dioxide (SiO2)

Petrified Wood

Silicified wood (Quartz/Chalcedony replacement of organic matter)

Petrified Wood

Silicified Wood (primarily SiO2)

Likely weathered gray stone or chert fragment

Uncertain; possibly microcrystalline quartz (SiO₂)-rich chert

Petrified Wood

Silicified Wood (primarily SiO2)

Zircon

Zirconium Silicate (ZrSiO₄)

Tektite

Natural impact glass