Petrified Wood

Physical Properties

Hardness: 6.5–7 on Mohs scale. Color: Tan, white, grey, brown. Luster: Vitreous to waxy. Structure: Trigonal (microcrystalline quartz). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.9.

Formation & Geological History

Formed through permineralization where organic wood materials are replaced by silica (chalcedony/quartz) over millions of years. This specimen likely dates from the Triassic to the Cenozoic era, occurring in sedimentary environments like floodplains and volcanic ash deposits.

Uses & Applications

Used primarily for lapidary work, jewelry making (cabochons), interior decoration (tabletops, bookends), and as educational geological specimens.

Geological Facts

Petrified wood is the state gemstone of several US states including Arizona and Washington. The cell structure of the original tree is often perfectly preserved, allowing paleobotanists to identify the specific extinct species of the tree.

Field Identification & Locations

Identify in the field by looking for distinct bark-like textures on the exterior or internal ring structures combined with a stony, glass-like fracture. Commonly found in areas with past volcanic activity or ancient drainage basins like the western United States, Madagascar, and Indonesia.

Identified on: 4/14/2026

Mode: Standard