sedimentary

Petrified Wood

Silicified wood (primarily SiO2)

Hardness: 6.5–7 (Mohs scale); Color: Brown, red, yellow, and tan; Luster: Vitreous to dull; Crystal structure: Microcrystalline quartz; Specific Gravity: 2.6–2.9.

Hardness: 6
Color: Brown, red, yellow, and tan
Luster: Vitreous to dull

Identified June 23, 2026More sedimentary →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6.5–7 (Mohs scale); Color: Brown, red, yellow, and tan; Luster: Vitreous to dull; Crystal structure: Microcrystalline quartz; Specific Gravity: 2.6–2.9.

Formation & geological history

Formed through permineralization, where organic remains of trees are replaced by minerals (usually silica) while retaining the original structure. Commonly dates from the Triassic to the Tertiary periods (200 to 20 million years ago).

Uses & applications

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

Geological facts

Famous locations include the Petrified Forest National Park in Arizona. In some cases, precious stones like opal can replace the wood fibers instead of quartz, creating 'opalized wood'.

Field identification & locations

Identify by looking for bark textures and growth rings preserved in stone. Found globally in ancient riverbeds or volcanic ash deposits. Collectors look for high color contrast and preservation of cellular detail.