metamorphic
Petrified Wood
Silicified Wood (SiO2)
Hardness: 6.5–7 on the Mohs scale; Color: typically browns, grays, and whites with visible growth rings; Luster: waxy to vitreous; Crystal structure: Trigonal (microcrystalline/cryptocrystalline); Specific gravity: 2.6–2.9.
- Hardness
- 6
- Luster
- waxy to vitreous
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Physical properties
Hardness: 6.5–7 on the Mohs scale; Color: typically browns, grays, and whites with visible growth rings; Luster: waxy to vitreous; Crystal structure: Trigonal (microcrystalline/cryptocrystalline); Specific gravity: 2.6–2.9.
Formation & geological history
Formed through permineralization, where organic remains are replaced by silica (usually chalcedony or quartz) over millions of years after being buried in sediment or volcanic ash. Common examples range from the Carboniferous to the Neogene periods.
Uses & applications
Used in high-end furniture (tabletops), jewelry (cabochons), interior decor, and as popular specimens for geological collections.
Geological facts
Famous locations include the Petrified Forest National Park in Arizona. Sometimes the cellular structure of the wood is so perfectly preserved that the specific tree genus can be identified under a microscope.
Field identification & locations
Identify in the field by looking for bark textures on the exterior and visible tree rings or wood grain on polished surfaces. It is much heavier and harder than actual wood and will not scratch with a steel knife. Common in volcanic ash beds and ancient river deltas.
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