mineral

Petrified Wood

Silicified wood (primarily Quartz/Chalcedony, SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish-orange; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9

Hardness: 6
Color: Brown, tan, reddish-orange
Luster: Dull to waxy

Identified June 16, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish-orange; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9

Formation & geological history

Formed through permineralization where organic wood materials are replaced by silica (chalcedony/opal) in an anaerobic environment, often buried by volcanic ash or river sediments. Most Western US specimens date from the Eocene to Miocene epochs (approx. 15-50 million years old).

Uses & applications

Used primarily for lapidary work, jewelry (cabochons), interior decor (tabletops, bookends), and as teaching or museum specimens.

Geological facts

The Oregon Cascades and Willamette Valley region are famous for Eocene petrified wood. These specimens often preserve the cellular structure of the original tree, such as annual growth rings and bark textures.

Field identification & locations

Identify by looking for wood-like grain, knots, and bark textures in a heavy, stony material that cannot be scratched by a steel knife. Common in the Holley and Sweet Home areas near the user's coordinates.

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