Petrified Wood (Agatized / Opalized Wood)
Indeterminate woody plant species (cf. Araucarioxylon, Taxodioxylon, or various ancient hardwood genera depending on region of origin) • Body fossil / Mineralized replacement fossil (Plant material)
Geological Period
Likely Paleogene to Neogene (Eocene - Miocene) or Mesozoic (Jurassic - Cretaceous)
Estimated Age
15 to 150 million years
Preservation Type
Permineralization and permineralized replacement by cryptocrystalline quartz (agate/chalcedony) and common opal, preserving internal volume without shrinkage.
Condition Assessment
Fair to Good; fragmentary rough specimen featuring natural exposed fractures showing glassy interior mineral structure.
Taxonomic Classification
Kingdom: Plantae, Tracheophyta (Vascular plants), Spermatopsida (Seed plants), Coniferophyta/Angiospermae (Unassigned conifer or hardwood wood structure)
Morphological Description
Fragmentary rough chunk showing outer bark/cambium layer texture on the exterior surface. The core exhibits microcrystalline silica mineralization with a glassy, conchoidal fracture pattern. Cellular wood grain structures are visible along the outer edges where organic wood texture transitions into silica replacement.
Rock Matrix
Ferruginous sandstone or volcanic ash deposit crust on outer layer; inner section completely replaced by chalcedonic silica/agate and minor iron oxide staining.
Formation & Location
Commonly sourced from volcanic mudflow/ash beds such as the Green River Formation (Wyoming, USA), Columbia River Basalt Group (Oregon/Washington, USA), or Madagascar fossil wood deposits.
Size & Dimensions
Approximately 6 to 9 cm (2.5 to 3.5 inches) across, representing a broken piece/nodule of a larger petrified branch or log.
Value & Rarity
Estimated Market Value
$10 - $25 USD
Auction Estimate
$15 - $30 USD
Rarity Assessment
Common (petrified wood is abundant globally, though high-grade agate/opal replacement pieces are prized by lapidaries and collectors).
Scientific Significance
Demonstrates silica permineralization mechanisms where organic carbonaceous matter is systematically replaced by dissolved silica from ground water or volcanic ash, preserving paleobotanical structures.
Preparation Recommendations
No chemical treatment required; specimen can be lapidary sliced and face-polished to reveal fine internal rings, color banding, and cell detail under magnification. Store in a dry, room-temperature environment.
Notable Features
High degree of silica saturation yielding glossy, conchoidal interior fracture surfaces with rich amber, brown, and dark mossy-green coloration contrasting against a dark brownish outer rind.