Petrified wood is fossilized wood with the mineral composition of jasper or chalcedony - 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.
Petrification of wood occurs only where trees are quickly covered with fine-grained sedimentary rock after their death- their outer structure therefore preserved in a negative form within the enclosing rock. Circulating waters loosen and decompose the wood and replace it gradually with mineral substances. This process occurs so that either the inner structural elements of the wood, the annuals rings, the structure of the cells, even wormholes, are preserved or sometimes the structure is completely changed in crystallization.
These pieces are from South East Queensland - mainly from the Chinchilla and Dalby regions. The sedimentary rocks of the Kumbarilla beds - aging from Jurassic to Lower Cretaceous age- underlie both these areas which is what accomodated the petrification of the wood in this area after the death of the trees.
Moh's Hardness Scale: 6.5 to 7.0 Mohs.
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