fossil

Polished petrified wood (agate/chalcedony replacement)

Silicified wood, chiefly microcrystalline quartz (SiO₂), often with iron-oxide coloration

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; brown, orange, gray, and cream coloration; waxy to glassy luster; cryptocrystalline quartz with no obvious cleavage; typically dense, with specific gravity around 2.5–2.7. The image shows a polished, irregular fragment with wood-like fibrous or cellular patterning.

Identified September 14, 2026More fossil →

Explore Polished petrified wood (agate/chalcedony replacement) in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

At a glance

Common name: Polished petrified wood (agate/chalcedony replacement)
Scientific name: Silicified wood, chiefly microcrystalline quartz (SiO₂), often with iron-oxide coloration
Category: fossil
Identified: September 14, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a small common polished fragment; $30–$150 or more for vividly colored, well-preserved, high-quality material.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Buried wood was gradually replaced by silica-rich groundwater, preserving cellular structure; iron oxides produced the orange-brown colors. Most examples formed in volcanic or sedimentary deposits during the Mesozoic or Cenozoic eras, though age depends on locality.

Uses & applications

Used for cabochons, carvings, display specimens, bookends, and lapidary objects; attractive patterned pieces have modest jewelry and collecting value.

Geological facts

Petrified wood is a fossil rather than a conventional rock, although its silica composition makes it rock-like. Excellent preservation can reveal annual rings, vessels, and microscopic cellular anatomy.

Field identification & locations

Identify it by visible wood grain or cellular texture, very high hardness, and inability to scratch with a steel knife; common sources include Arizona, Oregon, Indonesia, Madagascar, and Argentina. Confirmation requires examination of grain and a locality history.