fossil

Petrified Wood

Silicified wood (Quartz/Chalcedony replacement of organic matter)

Hardness: 6.5-7 (Mohs); Color: Brown, tan, reddish-brown; Luster: Dull to waxy; Structure: Cryptocrystalline quartz preserving original wood grain and cellular structure; Specific Gravity: 2.6-2.9

Hardness: 6
Color: Brown, tan, reddish-brown
Luster: Dull to waxy

Identified July 14, 2026More fossil →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: Brown, tan, reddish-brown; Luster: Dull to waxy; Structure: Cryptocrystalline quartz preserving original wood grain and cellular structure; Specific Gravity: 2.6-2.9

Formation & geological history

Formed when plant material is buried by sediment and protected from decay by oxygen and organisms. Groundwater rich in dissolved solids flows through the sediment, replacing original plant material with silica, calcite, or pyrite over millions of years, most commonly during the Triassic or Cenozoic periods.

Uses & applications

Used in jewelry (cabochons), interior design (decorative bookends or table tops), and as a popular specimen for fossil collectors.

Geological facts

The largest concentration of petrified wood is in the Petrified Forest National Park in Arizona, USA. It is the state fossil of Washington and the state rock of Mississippi.

Field identification & locations

Identify by looking for wood-like textures such as bark patterns or growth rings combined with the hardness and weight of stone. Often found in areas with ancient volcanic ash or river sedimentary deposits.

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