fossil

Petrified wood

Silicified wood, chiefly microcrystalline quartz (SiO₂)

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque brown, black, tan, and reddish bands with a dull to waxy luster. It preserves wood grain and cellular texture, but the visible piece appears heavily fractured and weathered rather than highly polished.

Identified August 11, 2026More fossil →

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Physical properties

Formation & geological history

Buried wood was gradually replaced and infilled by silica-rich groundwater, preserving its structure; commonly formed in volcanic-ash-rich sediments during the Cenozoic, though older examples occur. Exact age and locality cannot be determined from the image.

Uses & applications

Used as a lapidary material for cabochons, carvings, bookends, and decorative specimens; less commonly used in construction because quality material is collectible.

Geological facts

The original organic matter is usually almost entirely replaced by quartz, chalcedony, or opal while retaining growth rings and sometimes microscopic cells. Iron and manganese impurities create red, yellow, brown, and black colors.

Field identification & locations

Look for recognizable wood grain, concentric growth rings, bark-like texture, and a quartz-like hardness; it should scratch glass but not be scratched by a steel knife. Common localities include Arizona, Oregon, Indonesia, Madagascar, and Argentina.