metamorphic
Petrified Wood
Silicified Wood (SiO2)
Hardness: 6.5–7 (Mohs scale); Color: Variegated browns, tans, and blacks; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None/Conchoidal fracture; Specific gravity: 2.6–2.9.
- Hardness
- 6
- Color
- Variegated browns, tans, and blacks
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5–7 (Mohs scale); Color: Variegated browns, tans, and blacks; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None/Conchoidal fracture; Specific gravity: 2.6–2.9.
Formation & geological history
Formed through permineralization, a process where organic material is replaced by minerals (usually silica) while retaining original cellular structure. This specimen likely dates from the Mesozoic or Cenozoic eras and formed in low-oxygen environments such as river deltas or volcanic ash beds.
Uses & applications
Used primarily for lapidary work, jewelry (cabochons), interior decor (tabletops, bookends), and as educational geological specimens.
Geological facts
Famous locations include the Petrified Forest National Park in Arizona, USA. Despite being a 'rock,' it is technically a fossil. The colors are caused by trace elements; iron creates reds and oranges, while manganese produces blacks and purples.
Field identification & locations
Identify in the field by looking for distinct bark-like textures or visible concentric tree rings on fractured surfaces. It is much heavier and harder than actual wood and will not burn. Commonly found in areas with historical volcanic activity and sedimentary basins.
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