Petrified Wood
Silicified wood (Quartz var. Chalcedony) · Fossilized Mineral Specimen / Semi-Precious Gemstone
Crystal System
Trigonal/Microcrystalline; habit is massive, pseudomorphic after organic wood structures
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 with trace Fe2O3 (Iron Oxide) and organic carbon inclusions
Formation Process
Permineralization: Organic material is replaced by silica (chalcedony/quartz) through hydrothermal or groundwater action in anaerobic conditions
About This Crystal
A polished, rounded specimen displaying reddish-brown to cream colors. It is opaque with a vitreous to waxy luster, showing relict cellular wood structures and grain-like patterning.
Physical Characteristics
Color: Red, brown, yellow, and white; Streak: White; Cleavage: None; Fracture: Conchoidal to splintery; Specific Gravity: 2.58–2.91; Fluorescence: Often inert but can show green/yellow under SW UV if uranium or minerals like agate are present.
Optical Properties
Refractive Index: 1.544–1.553; Birefringence: 0.009; No pleochroism; Aggregates show no single-crystal optical phenomena except occasional chalcedony translucency.
Hardness & Durability
Origin Region
Arizona (Petrified Forest), Madagascar, and Indonesia; forms in fluvial sedimentary basins with volcanic ash
Hardness & Durability
Mohs Hardness: 6.5–7; Very tough and stable; excellent wearability for jewelry and decorative use.
Care & Maintenance
Clean with warm soapy water; safe for ultrasonic cleaning if no major fractures; avoid harsh chemicals like hydrofluoric acid; store away from harder stones like sapphire.
Rarity & Value
Common to uncommon; value depends on color saturation, presence of original wood detail, and size. Highly colorful specimens (Arizona Rainbow) are more valuable.
Special Characteristics
Pseudomorphism: Maintains the structural appearance of the original biological organic material while being 100% mineralized silica.
Lore & History
Historically used by Native Americans for amulets; symbolically associated with grounding, ancient ancestry, and the Root Chakra. It represents the transformation of the organic into the eternal.