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A Fossil Tree in Coal Measure Rock from Durham Coalfield

Fossil trees are quite frequently found in Coal Measures rocks, but this tree is different. It is a petrifaction: the actual woody tissue of the tree is mineralised with calcite and ankerite (calcium, magnesium, iron carbonate) so that the details of the internal structure of the trunk are preserved, in places including the tiny individual cells. The internal structure of the tree trunks show up when cut into individual cells whilst the individual structure of the tree trunks show up well when cut with a rock-saw. The wood was first mineralised with calcite when the empty dead cells were filled with mineral, leaving the organic cell walls intact. Subsequently the mineralised wood underwent recrystallisation that destroyed much of the original plan structure and produced a root-like pattern composed of radiating crystals. It is circular patches of radiating crystals of calcite that look so attractive in the polished cross-sections (http://cordaites.com/)