sedimentary
Petrified Wood
Silicified wood (Quartz/Chalcedony replacement of cellulose)
Hardness: 6.5-7.0 (Mohs scale); Color: Variegated brown, tan, white, and gray; Luster: Vitreous to waxy; Crystal structure: Microcrystalline; Cleavage: None; Specific Gravity: 2.6-2.9
- Hardness
- 6
- Color
- Variegated brown, tan, white, and gray
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7.0 (Mohs scale); Color: Variegated brown, tan, white, and gray; Luster: Vitreous to waxy; Crystal structure: Microcrystalline; Cleavage: None; Specific Gravity: 2.6-2.9
Formation & geological history
Formed through permineralization where organic wood materials are replaced by minerals (usually silica) while retaining the original structure. Commonly dates from the Triassic to the Tertiary periods.
Uses & applications
Used primarily for decorative objects, jewelry (cabochons), collection specimens, and interior design accents such as bookends and tabletops.
Geological facts
The Arizona Petrified Forest is the most famous location; the process occurs in the absence of oxygen to prevent rotting before minerals can saturate the wood cells.
Field identification & locations
Look for visible tree ring patterns or bark-like textures that are stone-hard. Found globally in ancient riverbeds and volcanic ash deposits. Collectors value pieces with clear cellular preservation.
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