fossil

Banded agate (likely petrified wood)

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

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; translucent gray, cream, yellow, orange, and brown bands; waxy to vitreous luster; cryptocrystalline quartz replacing wood tissues, with no prominent cleavage. The vertically oriented banding and bark-like outer zone strongly suggest fossil wood rather than ordinary agate.

Identified August 14, 2026More fossil →

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Physical properties

Formation & geological history

Formed when buried wood was progressively replaced by silica-rich groundwater, commonly during volcanic or sedimentary burial; iron and manganese produced the warm colors. Exact age and locality cannot be determined from the image, but many examples are Mesozoic to Cenozoic.

Uses & applications

Used for polished slabs, cabochons, carvings, bookends, and decorative specimens; durable silicified wood is also used as ornamental stone.

Geological facts

Wood grain, growth-ring patterns, cellular textures, and a contrasting bark rind are diagnostic of petrified wood. Agatized varieties may preserve microscopic anatomy in remarkable detail.

Field identification & locations

Look for preserved grain or cells, curved/concentric banding, and silica-like hardness; a steel file should not easily scratch it, while quartz can scratch glass. Common sources include Arizona, Oregon, Washington, Indonesia, Madagascar, and Argentina.