Petrified Wood
Silicified Wood (Quartz var. Chalcedony pseudomorph) · Organic Gem / Mineral Specimen / Decorative Stone
Crystal System
Trigonal (Microcrystalline); habit is pseudomorphic after organic tree structures, often showing bark-like textures or rings.
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2 (Silicon Dioxide) with trace Fe2O3 (Iron Oxide) and Carbon
Formation Process
Permineralization (Sedimentary/Hydrothermal); organic matter is buried and replaced atom-by-atom by silica-rich groundwater under low pressure.
About This Crystal
Opaque, wood-like appearance with visible fibrous texturing. Dull to waxy luster. Color ranges from earthy greys and browns to reds depending on mineral impurities.
Physical Characteristics
Grey-brown body color, white streak, no cleavage, conchoidal to splintery fracture, specific gravity 2.6–2.9, non-fluorescent.
Optical Properties
Isotropic to weakly anisotropic; Refractive Index 1.54–1.55; usually opaque so birefringence and pleochroism are not visible.
Hardness & Durability
Origin Region
Arizona (Petrified Forest National Park), Madagascar, Indonesia; found in fluvial or volcanic sedimentary basins.
Hardness & Durability
Mohs hardness 6.5–7; very tough and stable; excellent wearability for jewelry or display.
Care & Maintenance
Wash with warm soapy water; avoid harsh acids like hydrofluoric; generally resistant to fading but store away from high heat.
Rarity & Value
Common to Uncommon; value determined by preservation of wood grain, color intensity, and size. High-quality opalized wood is much rarer.
Special Characteristics
Pseudomorphism; retains the external and internal cellular structure of the original biological organism in stone.
Lore & History
Used by ancient Romans and Greeks; traditionally associated with grounding, ancient ancestry, and Earth's history. Believed to provide stability during times of change.