Petrified Wood

Hardness: 6.5-7 (Mohs scale), Color: Brown, tan, reddish-brown, Luster: Vitreous to dull, Crystal structure: Cryptocrystalline (chalcedony/quartz), Specific Gravity: 2.6-2.9

Formed via permineralization where organic wood materials are replaced by minerals (usually silica) while retaining original structure; commonly from the Triassic to Cenozoic eras in sedimentary environments like river basins and volcanic ash beds.

Used in ornamental lapidary work, jewelry (cabochons), decorative furniture (tables), and as highly sought-after display specimens for collectors.

The process preserves the microscopic details of the wood such as tree rings and cell structure. The presence of trace elements like manganese or iron creates the vibrant colors. Arizona's Petrified Forest National Park contains one of the world's largest concentrations.

Identify by looking for wood-like grain patterns, tree rings, or bark textures on a stone that is much heavier than wood and cannot be scratched by a steel knife. Common in the Western US, Madagascar, and Indonesia.