Petrified Wood

Physical Properties

Hardness: 6.5–7 (Mohs scale); Color: Brown, tan, reddish-orange, and black; Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline (Microcrystalline Quartz); Specific Gravity: 2.6–2.9

Formation & Geological History

Formed through permineralization, a process where organic material is replaced by minerals (usually silica) while retaining the original structure of the wood. This typically occurs when wood is buried under volcanic ash or sediment millions of years ago, often during the Triassic to Tertiary periods.

Uses & Applications

Used primarily for jewelry (cabochons), interior decor (tabletops, bookends), fossil collecting, and lapidary art.

Geological Facts

Famous locations include the Petrified Forest National Park in Arizona, which contains wood from the Late Triassic epoch (roughly 225 million years old). The colors are determined by trace elements like iron (red/yellow), manganese (pink/purple), and cobalt (blue).

Field Identification & Locations

Identify in the field by looking for wood-like texture, grain, and bark patterns preserved in stone. It is commonly found in areas of historical volcanic activity or sedimentary basins. Collectors should look for high-contrast banding and intact cellular detail.

Identified on: 4/21/2026

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