Petrified Wood

Physical Properties

Hardness: 6.5–7 (Mohs scale); Color: Brown, tan, reddish-brown; Luster: Vitreous to waxy; Structure: Cryptocrystalline quartz preserving original wood cellular structure; 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) while buried in sediment. This specimen likely dates from the Triassic to the Pleistocene period, common in volcanic ash or river delta environments.

Uses & Applications

Used primarily for lapidary work, jewelry making (cabochons), ornamental display pieces, and as a educational fossil specimen.

Geological Facts

Petrified wood is a fossil in which the organic remains have been replaced by minerals. It is the state gemstone of Arizona, home to the famous Petrified Forest National Park.

Field Identification & Locations

Identify in the field by looking for distinct bark-like textures or rings on the exterior combined with a heavy, rock-like weight and a glassy, chert-like fracture. Often found in areas with history of volcanic activity and ancient riverbeds.

Identified on: 4/19/2026

Mode: Standard