Petrified Wood

Physical Properties

Hardness: 6.5–7 (Mohs scale); Color: Brown, black, tan, and grey with visible growth rings; Luster: Vitreous to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6–2.9

Formation & Geological History

Formed through permineralization, a process where organic material is replaced by minerals (usually silica) over millions of years. This specimen likely dates from the Triassic to Eocene epochs, formed in anaerobic conditions under volcanic ash or sediment.

Uses & Applications

Used primarily for lapidary work, jewelry making (cabochons), interior decor (tabletops, bookends), and as a popular collectable for geological enthusiasts.

Geological Facts

Petrified wood is the state fossil of Arizona, Mississippi, and Washington. It can preserve cellular details of the original tree so accurately that the species of tree can often be identified under a microscope.

Field Identification & Locations

Identify in the field by looking for woody textures, bark patterns, or growth rings in a rock that is heavy and hard enough to scratch steel. Commonly found in areas with past volcanic activity following heavy sedimentation.

Identified on: 4/19/2026

Mode: Standard