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Question of the Week / QotW - 09.01.18 - Fossilised Fence Posts?
« on: 16/01/2009 06:09:22 »
Permineralisation is the correct term for this process. This happens as Carbon (C) in the wood is replaced by Silicon (Si). It turns out that Si has a +4 valance state the same as C, so because it has similar properties and is fairly similar in size this chemical replacement is sometimes possible. As I have heard this process only takes place in a few very specific settings where wood is rapidly buried before it has an opportunity to decompose and it must be buried in an Si rich setting. The best mechanism for this to occur is to have wood buried by material erupted from a volcano that has a chemical composition high in quartz (SiO2). When this eruption takes place the rock that is deposited from the volcano is probably going to be known as rhyolite, the extrusive equivalent to granite, if the rock remains warm/hot for a time the Si may be able to migrate into the structure of the cell in the wood where the Si will displace the C and leave behind permineralized wood.