Rock Identifier
Petrified Wood (Agatized or Silicified Wood (SiO2)) — fossil
fossil

Petrified Wood

Agatized or Silicified Wood (SiO2)

AI-generated identification · may be incorrect

Hardness 6.5-7 (Mohs scale), colors vary (often brown, red, yellow, grey), waxy to dull luster, microcrystalline structure, no cleavage, specific gravity ~2.6.

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Physical properties

Hardness 6.5-7 (Mohs scale), colors vary (often brown, red, yellow, grey), waxy to dull luster, microcrystalline structure, no cleavage, specific gravity ~2.6.

Formation & geological history

Formed when plant material is buried by sediment and protected from decay by oxygen and organisms. Then, groundwater rich in dissolved solids flows through the sediment, replacing the original plant material with silica, calcite, pyrite, or another inorganic material such as opal.

Uses & applications

Popular among collectors, used in jewelry, lapidary arts, and sometimes in furniture or decorative items.

Geological facts

Petrified wood is the state fossil of Washington and North Dakota. The colors are determined by trace elements (e.g., iron causes red/brown, copper/cobalt/chromium causes green/blue).

Field identification & locations

Identify by looking for wood grain, bark textures, or tree rings preserved in a stone-like material. Commonly found in areas with past volcanic activity and forests, such as the Petrified Forest National Park in Arizona.

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