metamorphic
Petrified Wood (Silicified Wood)
Silicified Wood / Silicon Dioxide (SiO2)
Hardness: 6.5–7 on Mohs scale; Color: Red, brown, tan, and grey with distinct wood-grain patterns; Luster: Vitreous to waxy when polished; Structure: Cryptocrystalline quartz; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Red, brown, tan, and grey with distinct wood-grain patterns
- Luster
- Vitreous to waxy when polished
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Physical properties
Hardness: 6.5–7 on Mohs scale; Color: Red, brown, tan, and grey with distinct wood-grain patterns; Luster: Vitreous to waxy when polished; Structure: Cryptocrystalline quartz; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through permineralization where organic wood material is replaced by minerals (usually silica) in anaerobic conditions. This specimen likely dates to the Triassic period (approx. 200–250 million years ago) from the Chinle Formation.
Uses & applications
Used primarily for decorative lapidary items, jewelry (cabochons), furniture (slices for tables), and as high-value geological display specimens for collectors.
Geological facts
In some specimens, the replacement is so perfect that cell structures and annual rings are visible under a microscope. The Arizona Petrified Forest is one of the most famous sites globally where this occurs naturally.
Field identification & locations
Identify in the field by looking for rock sections that retain the external bark texture and internal ring patterns of a tree trunk. Commonly found in Arizona (USA), Madagascar, and Indonesia. Look for quartz crystals inside vugs (like seen in the photo).
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