Petrified Wood
Chalcedony var. Silicified Wood · Mineral Specimen / Semi-Precious Gemstone
Crystal System
Trigonal/Microcrystalline; typically massive/pseudomorphous habit after wood cellular structure
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2 (Silicon Dioxide) with organic carbon and traces of Iron, Manganese, and Aluminum oxides
Formation Process
Permineralization (Diagenesis); organic materials are replaced by silica from groundwater or volcanic ash over millions of years
About This Crystal
Opaque, tan to brownish-grey specimen displaying linear grain patterns indicative of original wood lignin. Luster is dull to waxy on fractures, with distinct dark horizontal banding.
Physical Characteristics
Color: Tan, beige, and dark charcoal grey; Streak: White; Fracture: Conchoidal to splintery; Specific Gravity: 2.6–2.9; Non-fluorescent usually.
Optical Properties
Opaque to occasionally translucent at edges; Refractive Index: 1.544–1.553; No pleochroism or dispersion visible due to opacity.
Hardness & Durability
Origin Region
United States (Arizona, Oregon), Madagascar, Indonesia; found in sedimentary basins and volcanic ash beds
Hardness & Durability
Mohs Hardness: 6.5–7; Toughness: Good (being a form of chalcedony/agate); High stability for jewelry and display.
Care & Maintenance
Safe with warm soapy water; avoid prolonged exposure to harsh acids; store separately from softer minerals to prevent scratching.
Rarity & Value
Common; Value depends on the preservation of cellular detail and color vibrancy; this piece is a raw field specimen of moderate value.
Special Characteristics
Pseudomorphism; the specimen retains the macroscopic structure of biological wood fiber despite being entirely mineralized.
Lore & History
Historically used as amulets in ancient Rome and Etruria. Traditionally associated with grounding, ancient ancestry, and patience in lithotherapy.