sedimentary
Petrified Wood
Silicified wood (principally SiO2)
Hardness: 6.5-7 (Mohs); Color: Brown, red, orange, and tan; Luster: Dull to waxy/vitreous; Structure: Microcrystalline quartz (Chalcedony/Jasper) preserving cellular wood structure; Cleavage: None; Specific Gravity: 2.6-2.9
- Hardness
- 6
- Color
- Brown, red, orange, and tan
- Luster
- Dull to waxy/vitreous
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Brown, red, orange, and tan; Luster: Dull to waxy/vitreous; Structure: Microcrystalline quartz (Chalcedony/Jasper) preserving cellular wood structure; Cleavage: None; Specific Gravity: 2.6-2.9
Formation & geological history
Formed through permineralization where organic wood material is replaced by minerals, typically silica from volcanic ash, while buried under sediment. Processes often date back to the Triassic or Cenozoic periods.
Uses & applications
Used in high-end furniture (tabletops), lapidary work, jewelry (cabochons), and as museum or private collection display specimens.
Geological facts
Petrified wood is the state gemstone of Washington and Mississippi. It occurs when a tree is buried in an environment lacking oxygen, preventing aerobic decomposition and allowing minerals to seep in.
Field identification & locations
Identify by looking for bark textures and ring patterns on a material that feels significantly heavier than wood and is cold to the touch. Commonly found in Arizona (Petrified Forest National Park), Oregon, and Madagascar.
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