Mineral Guide · Material
Petrified wood is fossil wood in which mineral-rich fluids replaced or infilled organic tissue, preserving growth rings, pores and grain as stone.
Petrified wood is fossil wood in which mineral-rich fluids replaced or infilled organic tissue, preserving growth rings, pores and grain as stone.
Reference formula: SiO2. Petrified wood is a multi-phase fossil material rather than one mineral. Quartz, chalcedony, opal and other phases may coexist, so no single artificial lattice is assigned. Petrified wood is classified with silicates and has a not applicable crystal system. Typical hardness is 6.5–7 on the Mohs scale and specific gravity is approximately 2.2–2.8.
Typical colours include brown, red, cream, black, grey. The usual fibrous, massive, banded habit and waxy, vitreous, dull lustre help describe a specimen, but colour alone is not diagnostic.
Petrified wood forms in or is associated with burial, silica-rich groundwater, volcanic ash environments and long-term mineral replacement. Important documented localities include Arizona, Madagascar, Indonesia, Argentina, Australia and many sedimentary basins.
Petrified wood is a strong commercial bridge between geology and natural history: the buyer can read biological structure that has been preserved by mineral replacement.
Avoid harsh acids and thermal shock; preserve the natural polish and document whether resin or stabilisation has been used.
Reviewed by NotOnlyRocks Editorial Team
Last reviewed: 28 August 2026
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