Rock Identifier
Polished petrified wood (Silicified fossil wood, chiefly microcrystalline quartz (SiO₂)) — fossil
fossil

Polished petrified wood

Silicified fossil wood, chiefly microcrystalline quartz (SiO₂)

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; polished vitreous-to-waxy luster, opaque brown, tan, cream, and purple coloration, with preserved wood grain and silica replacing cell tissues. No prominent cleavage; specific gravity typically 2.5–2.7.

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Physical properties

Hardness about 6.5–7 Mohs; polished vitreous-to-waxy luster, opaque brown, tan, cream, and purple coloration, with preserved wood grain and silica replacing cell tissues. No prominent cleavage; specific gravity typically 2.5–2.7.

Formation & geological history

Ancient wood was buried in oxygen-poor sediment and gradually replaced by silica-rich groundwater, preserving cellular structure. Most commercial material formed during the Mesozoic or Cenozoic, though age varies by locality.

Uses & applications

Used for cabochons, tumbled stones, carvings, bookends, and decorative slabs; attractive lapidary pieces have modest collector value.

Geological facts

The visible banding and branching grain are characteristic of fossilized wood rather than ordinary jasper. Purple zones may reflect manganese or iron-bearing impurities.

Field identification & locations

Identify it by recognizable wood grain, lack of organic softness, high silica hardness, and resistance to scratching by steel. Common sources include Arizona, Oregon, Indonesia, Madagascar, and Argentina.

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