sedimentary
Petrified Wood
Silicified wood (Quartz/Chalcedony/SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, cream, reddish; Luster: Waxy to dull (stony); Crystal structure: Microcrystalline (Cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.9.
- Hardness
- 6
- Color
- Brown, tan, cream, reddish
- Luster
- Waxy to dull (stony)
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, cream, reddish; Luster: Waxy to dull (stony); Crystal structure: Microcrystalline (Cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.9.
Formation & geological history
Formed through permineralization where organic wood material is replaced by minerals, typically silica (chalcedony or quartz), while retaining the original cellular structure. This specimen likely dates from the Triassic to the Cenozoic era, forming in sedimentary basins or volcanic ash beds.
Uses & applications
Used for ornamental decoration, jewelry (cabochons), lapidary art, and popular as geological collectibles.
Geological facts
Petrified wood is the state fossil of Washington and several other US states. The Petrified Forest National Park in Arizona is one of the world's most famous locations for these specimens.
Field identification & locations
Identify by looking for bark textures and growth rings preserved in stone. Found globally, especially in Arizona, Oregon, and Madagascar. Collectors look for high color contrast and preservation of wood grain detail.
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