metamorphic
Petrified Wood
Silicified Wood (SiO2)
Hardness: 7 onto Mohs scale; Color: Brown, grey, black, and tan (stained by iron and manganese); Luster: Waxy to vitreous; Crystal structure: Trigonal/Amorphous (microcrystalline Quartz/Chalcedony); Cleavage: None; Specific Gravity: 2.6-2.9.
- Hardness
- 7 onto Mohs scale
- Color
- Brown, grey, black, and tan (stained by iron and manganese)
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 onto Mohs scale; Color: Brown, grey, black, and tan (stained by iron and manganese); Luster: Waxy to vitreous; Crystal structure: Trigonal/Amorphous (microcrystalline Quartz/Chalcedony); Cleavage: None; Specific Gravity: 2.6-2.9.
Formation & geological history
Formed via permineralization, where organic remains are replaced by minerals (silica) from groundwater over millions of years. Examples range from the Devonian to the Pleistocene epochs, commonly found in sedimentary basins with volcanic ash deposits.
Uses & applications
Used in lapidary work, jewelry (cabochons), interior design (polished slabs, tabletops), and as a popular geological collectible due to its unique preservation of plant structures.
Geological facts
Petrified wood is the state stone of Washington and the state fossil of Arizona. The Arizona Petrified Forest is one of the world's most famous sites, featuring trees that lived over 225 million years ago.
Field identification & locations
Identify in the field by looking for bark-like textures or growth ring patterns on a high-hardness rock that won't scratch with a steel blade. Common in 'badlands' terrain in the American West (Arizona, Utah, Wyoming).
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