sedimentary
Petrified Wood
Silicified Wood (SiO2)
Hardness: 6.5 - 7 on Mohs scale. Colors: Red, orange, brown, tan from iron and manganese oxides. Luster: Vitreous to dull. Structure: Microcrystalline quartz, often preserving cellular tracheid structures.
- Hardness
- 6
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5 - 7 on Mohs scale. Colors: Red, orange, brown, tan from iron and manganese oxides. Luster: Vitreous to dull. Structure: Microcrystalline quartz, often preserving cellular tracheid structures.
Formation & geological history
Formed via permineralization during the Mesozoic or Cenozoic eras. Organic matter is replaced by silica (typically quartz or agate) in an anaerobic environment, often buried under volcanic ash or river sediments.
Uses & applications
Used for lapidary work, jewelry making (cabochons), ornamental furniture, bookends, and as a popular collector's specimen.
Geological facts
The Arizona Petrified Forest is one of the world's most famous locations, featuring logs from the Triassic period (approximately 225 million years ago). Some specimens preserve growth rings so well they can be used for dendrochronology studies.
Field identification & locations
Identify in the field by looking for bark-like textures on the exterior and characteristic wood grain or cell structures on the interior. Use a hardness test (it will scratch glass). Common in dry, eroded landscapes or badlands.
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