fossil

Petrified wood

Silicified fossil wood, commonly quartz/chalcedony (SiO₂) replacing woody tissue

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; brown, tan, and gray banding preserves wood grain, with a dull to subtly vitreous luster. Typically microcrystalline quartz, compact, heavy, and lacking obvious cleavage; apparent pores and growth textures follow the original wood.

Identified September 5, 2026More fossil →

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Physical properties

Formation & geological history

Groundwater gradually replaced buried wood with silica, often preserving cellular structure; most examples range from tens of thousands to hundreds of millions of years old. It forms in volcanic-ash-rich sediments, floodplains, and other silica-bearing burial environments.

Uses & applications

Used for lapidary cabochons, carvings, bookends, ornamental slabs, and collecting; quality patterned pieces can be polished as decorative stone.

Geological facts

Petrified wood is a fossil, not merely a weathered branch: mineral replacement can preserve annual rings and microscopic anatomy in remarkable detail.

Field identification & locations

Identify it by recognizable wood grain, a stone-like weight, absence of fresh organic fibers, and inability to bend or splinter like wood; a steel file should barely scratch it. Common sources include Arizona, Utah, Oregon, Indonesia, Madagascar, and Australia.