Petrified Wood (Fossilized Wood)

Big Photo

Arizona, USA
20.95 carats
© wolfelapidary.com

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.

Petrified Wood Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
 

Petrified Wood Gemstones by Size

This table shows distribution of Petrified Wood gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:11.00 cts
Heaviest:72.60 cts
Average:30.26 cts
Total photos:20
Do you have a larger Petrified Wood? Why not upload a photo?
11.00ct to 17.16ct17.16ct to 23.32ct23.32ct to 29.48ct29.48ct to 35.64ct35.64ct to 41.80ct41.80ct to 47.96ct47.96ct to 54.12ct54.12ct to 60.28ct60.28ct to 66.44ct66.44ct to 72.60ct
General Information
A variety or type of:Chalcedony, which is a variety of Quartz
Chemical Formula
SiO
 
2
Walter Schumann, Gemstones of the world (2001)
Photos of natural/un-cut material from mindat.org
Physical Properties of Petrified Wood
Mohs Hardness6.5 to 7
Walter Schumann, Gemstones of the world (2001)
Specific Gravity2.58 to 2.91
Walter Schumann, Gemstones of the world (2001)
Cleavage QualityNone
Walter Schumann, Gemstones of the world (2001)
FractureUneven,Splintery
Walter Schumann, Gemstones of the world (2001)
Optical Properties of Petrified Wood
Refractive IndexAbout 1.54
Walter Schumann, Gemstones of the world (2001)
BirefringenceWeak or none
Walter Schumann, Gemstones of the world (2001)
PleochroismAbsent
Walter Schumann, Gemstones of the world (2001)
DispersionNone
Walter Schumann, Gemstones of the world (2001)
Colour
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)
TransparencyOpaque
Walter Schumann, Gemstones of the world (2001)
Fluorescence & other light emissions
Fluorescence (General)None
Walter Schumann, Gemstones of the world (2001)
Crystallography of Petrified Wood
Crystal SystemTrigonal
Walter Schumann, Gemstones of the world (2001)
HabitMicrocrystalline aggregate
Walter Schumann, Gemstones of the world (2001)
Geological Environment
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)
Further Information
Mineral information:Petrified Wood information at mindat.org
Significant Gem Localities
USA
 
  • Arizona
    • Navajo Co.
Gemstones of the world, Walter Schumann, 2001, p.148
        • Petrified Forest National Park
  • California
    • Kern Co.
      • Kramer District
    • Siskiyou Co.
      • Klamath Mts
        • Cinnabar Camp
U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.
  • Nevada
    • Humboldt Co.
Gemstones of the world, Walter Schumann, 2001, p.148
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