sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 Mohs; Color: Tan, cream, or light brown (in this specimen); Luster: Waxy to dull; Crystal structure: Cryptocrystalline (Microcrystalline Quartz); Cleavage: None; Specific Gravity: 2.6-2.9

Hardness: 6
Color: Tan, cream, or light brown (in this specimen)
Luster: Waxy to dull

Identified June 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization where organic wood materials are replaced by silica (usually chalcedony or opal) from groundwater while buried under sediment. This process can happen over millions of years, often in volcanic ash or river delta environments.

Uses & applications

Used primarily for ornamental purposes, lapidary art, jewelry (cabochons), and as museum or private collection display pieces.

Geological facts

Petrified wood is a fossil in which the organic remains have been replaced by minerals in the slow process of being turned to stone. Entire fossilized forests exist, such as the Petrified Forest National Park in Arizona, dating back about 225 million years to the Late Triassic.

Field identification & locations

Identify in the field by looking for bark-like textures or rings on a stone that is much harder than typical sedimentary rock. Common in Arizona, Madagascar, and Indonesia. Collectors look for well-preserved grain and vibrant mineral colors.