Wood Jasper

Hardness: 6.5-7 on Mohs scale. Color: Shades of brown, beige, tan, and grey, often with distinct bands or swirling patterns resembling wood grain. Luster: Dull to vitreous. Crystal structure: Cryptocrystalline (microscopic crystals). Cleavage: None, exhibits conchoidal fracture. Specific Gravity: 2.58-2.91.

Wood Jasper is a type of silicified wood, formed when organic wood matter is replaced by silica minerals, primarily chalcedony. This process of permineralization or replacement occurs when wood is buried under sediment and groundwater rich in dissolved silica permeates the wood's cellular structure. Over millions of years, the silica precipitates and crystalizes, preserving the original wood structure. The geological age can vary widely depending on the original wood and burial event, ranging from millions to hundreds of millions of years (e.g., Cenozoic to Paleozoic eras).

Primarily used in jewelry for beads, cabochons, and polished stones due to its attractive wood-like patterns. Also used in ornamental carvings, decorative objects, and occasionally in lapidary art.

While often called 'Wood Jasper', it's technically a form of petrified wood. True jasper is an opaque, impure variety of silica, usually red, yellow, brown or green in color. The 'wood' aspect refers to the preserved texture of ancient trees. The banding and swirling patterns are a result of variations in mineral deposition during the silicification process.

In the field, it can be identified by its hardness, fracture, and distinctive wood-grain patterns. Look for areas with ancient forests, volcanic ash deposits (which often provide silica-rich groundwater), or sedimentary formations where plant matter was once abundant. Common locations include the Petrified Forest National Park in Arizona, USA, as well as sites in Madagascar, Argentina, and Indonesia. Collectors look for pieces with well-preserved wood structure and interesting color variations and patterns.