metamorphic
Petrified Wood
Silicified wood (primarily Silicon Dioxide, SiO2)
Hardness: 6.5-7 (Mohs scale), Color: Brown, gray, tan with wood-grain textures, Luster: Dull to waxy or vitreous, Structure: Cryptocrystalline quartz preserving organic cellular structures, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.9
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Brown, gray, tan with wood-grain textures, Luster: Dull to waxy or vitreous, Structure: Cryptocrystalline quartz preserving organic cellular structures, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.9
Formation & geological history
Formed through permineralization where organic wood materials are replaced by minerals (usually silica) over millions of years. This specimen shows 'casting' or petrifaction common in the Triassic to Neogene periods.
Uses & applications
Used for ornamental purposes, lapidary art, jewelry (cabochons), interior design (bookends, tabletops), and as geological display specimens.
Geological facts
Petrified wood is the state fossil of Arizona. The process is so precise it can preserve individual tree rings and even microscopic cellular structures of the original plant matter.
Field identification & locations
Identify by looking for visible bark textures, tree ring patterns, or fibrous wood-like longitudinal grain combined with a stony, heavy feel. Found in sedimentary basins globally, notably Petrified Forest National Park, USA.
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