sedimentary
Petrified Wood
Silicified Wood (SiO2)
Hardness: 7.0 on Mohs scale. Color: Tan, white, gray, and brown. Luster: Vitreous to dull. Crystal structure: Amorphous to cryptocrystalline (chalcedony/quartz). Cleavage: None. Specific gravity: 2.6-2.9.
- Hardness
- 7
- Color
- Tan, white, gray, and brown
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7.0 on Mohs scale. Color: Tan, white, gray, and brown. Luster: Vitreous to dull. Crystal structure: Amorphous to cryptocrystalline (chalcedony/quartz). Cleavage: None. Specific gravity: 2.6-2.9.
Formation & geological history
Formed through permineralization where organic wood materials are replaced by minerals (usually silica) from groundwater while retaining the original structure. Generally occurs in sedimentary environments like fluvial deposits.
Uses & applications
Commonly used for lapidary work, jewelry, decorative ornaments, furniture (table tops), and as highly sought-after display specimens for collectors.
Geological facts
The process converts the wood to stone over millions of years. Famous locations include the Petrified Forest National Park in Arizona, which contains logs from the Late Triassic Period (about 225 million years ago).
Field identification & locations
Identify by looking for bark textures, growth rings, and wood grain preserved in a heavy, stony material. Commonly found in erosion-prone badlands and ancient volcanic ash beds.
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