Petrified Wood (Fossilized Wood)
Petrified wood is fossilized wood with the mineral composition of
jasper,
chalcedony and, less frequently,
opal; it consists of silicon dioxide only. The organic wood is not changed into stone, but only the shape and structural elements of the wood are preserved. The expert speaks of a pseudomorphosis of
chalcedony (or
jasper or
opal) after wood.
It is mostly used for ornamental objects and decorative pieces (tabletops, ashtrays, bookends), less frequently for jewelry purposes.
| General Information |
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| A variety or type of: | Chalcedony, which is a variety of Quartz |
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| Chemical Formula | Walter Schumann, Gemstones of the world (2001) |
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| Physical Properties of Petrified Wood |
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| Mohs Hardness | 6.5 to 7Walter Schumann, Gemstones of the world (2001) |
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| Specific Gravity | 2.58 to 2.91Walter Schumann, Gemstones of the world (2001) |
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| Cleavage Quality | NoneWalter Schumann, Gemstones of the world (2001) |
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| Fracture | Uneven,SplinteryWalter Schumann, Gemstones of the world (2001) |
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| Optical Properties of Petrified Wood |
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| Refractive Index | About 1.54Walter Schumann, Gemstones of the world (2001) |
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| Birefringence | Weak or noneWalter Schumann, Gemstones of the world (2001) |
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| Pleochroism | AbsentWalter Schumann, Gemstones of the world (2001) |
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| Dispersion | NoneWalter Schumann, Gemstones of the world (2001) |
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| Colour |
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| Colour (General) | Mostly dull gray or brown, sometimes red, pink, light brown, yellow, and even blue to violet.Walter Schumann, Gemstones of the world (2001) |
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| Transparency | OpaqueWalter Schumann, Gemstones of the world (2001) |
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| Fluorescence & other light emissions |
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| Fluorescence (General) | NoneWalter Schumann, Gemstones of the world (2001) |
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| Crystallography of Petrified Wood |
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| Crystal System | TrigonalWalter Schumann, Gemstones of the world (2001) |
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| Habit | Microcrystalline aggregateWalter Schumann, Gemstones of the world (2001) |
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| Geological Environment |
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| Where found: | Well-preserved petrification occurs only where trees after their death are quickly covered with fine-grained sedimentary rock. Thus the outer structure of the wood is preserved in a negative form within the enclosing rock. Circulating waters loosen and decompose the organic substances and replace them with mineral substances. Sometimes this process is successive (from removal and adding of substances) so that the inner structural elements of the wood, the annuals rings, the structure of the cells, even wormholes, are preserved. It can also happen that the appearance is totally changed by the crystallization process.Walter Schumann, Gemstones of the world (2001) |
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| Further Information |
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| Mineral information: | Petrified Wood information at mindat.org |
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| Significant Gem Localities |
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| USA | | |
| Gemstones of the world, Walter Schumann, 2001, p.148 | |
| U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia. | |
| Gemstones of the world, Walter Schumann, 2001, p.148 |
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