Permineralisation

Permineralisation, or permineralization, is a type of fossilization in which mineral-rich groundwater penetrates the porous tissues of dead organisms and deposits minerals within their interior spaces. The process often preserves the three-dimensional framework of the original organism rather than just a surface impression, producing a detailed internal replica.

The sequence typically begins after burial in sediment, when groundwater carrying dissolved minerals percolates through remains such as wood, bone, or shell. Minerals such as silica (as quartz or opal), calcite, pyrite, or apatite precipitate from the solution and fill pore spaces and voids. In many cases the original organic framework remains intact while minerals crystallize within it; in other cases the tissue is gradually replaced by minerals, though fine structural details can still be preserved.

Permineralisation is the most common mode of preserving hard tissues and can produce excellent three-dimensional representations. It is especially important for preserving bone and teeth in vertebrates, as well as fossilized wood and other plant materials. The degree of preservation depends on the chemistry of the infiltrating fluids, the porosity of the tissue, and the rate of burial and mineralization. Famous examples include petrified wood from silica-rich environments and fossil bones or shells that have been mineralized to retain detailed internal structures.

Permineralisation is distinct from replacement, where original material is dissolved and wholly replaced by minerals, and from other fossilization modes that favor surface impressions or carbon films. It provides valuable insights into ancient morphology, growth, and tissue organization.