sedimentary
Petrified Wood
Silicified Wood (primarily Chalcedony or Quartz, SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish-orange; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None; Specific Gravity: 2.6-2.9
- Hardness
- 6
- Color
- Brown, tan, reddish-orange
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish-orange; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None; 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 the original structure of the wood. This typically occurs in sedimentary environments under volcanic ash or water saturation, often dating back to the Mesozoic or Cenozoic eras.
Uses & applications
Used primarily for decorative furniture, lapidary items (cabochons), jewelry, and as educational geological or fossil specimens.
Geological facts
Famous locations include the Petrified Forest National Park in Arizona, which contains wood from the Triassic period (approx. 225 million years ago). Different colors are caused by trace elements: iron yields red/brown, manganese yields pink/orange, and copper/cobalt can yield greens or blues.
Field identification & locations
Identify in the field by looking for distinct bark-like textures, growth rings, and wood grain paired with high density and extreme hardness. Common in badlands or areas with high volcanic ash deposits.
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