1& 2*Randall S. Perry, 1Nicola McLoughlin, 3Bridget Y. Lynne, 4Mark Sephton, 2 Joan Oliver, 5Carole C.
Perry, 3Kathleen
1Earth Sciences,
2Planetary Science Institute,
3Department of Geology,
4Department of Earth Science and Engineering, South
Kensington Campus,
5Chemistry Division, The
6School of Geology and Geophysics,
7Department of Geological Sciences,
8Department of Microbiology,
* Randall.Perry@earth.ox.ac.uk , 44 (0)186 527 2069, perry@psi.edu, 1-206 543-6267
Biomineralization is the uptake of elements and their incorporation into mineral structures under direct biological control. It is the method by which most higher organisms form exo- or endoskeletons, directly precipitating minerals (e.g., silica, calcite, apatite). Yet minerals may also be induced and/or formed indirectly by biological activity e.g., altering local Eh-pH conditions. Certain minerals cannot be generated without pre-existing, biologically-produced organic matter. The complexation between inorganic materials while in the presence of the byproducts of dead organisms, profoundly affects chemical reactions which promote the formation of specific minerals. These indirectly-formed mineral products of biological activity might be more appropriately called organominerals.
Precise terminology is efficacious both in indicating the equivocal nature of new information and in possibly shaping the development and direction of future research. We present case studies of investigations that may have been misdirected because of terminology. Examples include our latest research, hot-spring siliceous deposits, desert varnish, endolithic trace fossils, stromatolites, and bacterial incrustations. It is necessary to make the distinction between minerals incorporated into functional structures directly by organisms and minerals complexed with organopolymers, and bio(organic), and/or organic compounds. This is important when ascertaining the presence of past life and considering questions such as the veracity of Archean fossils on Earth or evaluating whether evidence of life is preserved in meteorites or on other Planets. Successful interpretations rely on our ability to identify minerals that are direct indicators of life.
The extension of the term ‘organomineral’ to geobiology, provides a more precise definition of these minerals and a way of distinguishing them from biominerals.