sedimentary
Petrified Wood
Silicified Wood (SiO2)
Hardness of 6.5 to 7 on the Mohs scale, colors vary widely including brown, red, yellow, and grey due to mineral impurities, vitreous to waxy luster, amorphous crystal structure (microcrystalline quartz)
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, colors vary widely including brown, red, yellow, and grey due to mineral impurities, vitreous to waxy luster, amorphous crystal structure (microcrystalline quartz)
Formation & geological history
Formed through permineralization where organic plant material is buried in anoxic, mineral-rich sediment and groundwater replaces the original wood cells with silica over millions of years, typically dating from the Triassic period or older
Uses & applications
Used in lapidary arts, decorative items, jewelry, bookends, and highly valued by fossil and rock collectors
Geological facts
Petrified wood is the state fossil of several US states, including Washington and Arizona, and the Petrified Forest National Park contains one of the world's largest concentrations of it
Field identification & locations
Identified by retaining the original cellular structure and growth rings of wood while having the heavy weight, cold feel, and hardness of quartz; commonly found in river deposits, desert badlands, and sedimentary layers worldwide
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