New developments and discoveries in biomineralization have occurred almost continuously in the intervening decade since the previous IUGG quadrennial report on biomineralization and biomagnetism was published [ Kirschvink, 1983]. Biomineralization is widespread in the biosphere and over 60 different inorganic minerals are produced by a variety of organisms from bacteria to humans [ Lowenstam and Weiner, 1989]. The literature on biomineralization is interdisplinary, combining research in microbiology, biotechnology, physics, geology, and paleomagnetism. For paleomagnetism and rock magnetism, iron biomineralization of magnetic minerals is of prime importance. From a paleomagnetism perspective, biogenic magnetic minerals can be deposited in sediments and acquire a natural remanent magnetization that preserves a record of the ancient geomagnetic field. From a rock magnetism perspective, biogenic magnetic minerals provide novel sources of magnetic material for experimental studies in fine particle magnetism. Both perspectives are interrelated through a common goal of developing magnetic techniques to detect biogenic magnetic minerals in sediments and soils. For example, the extent to which iron biominerals contribute to the fine-grained magnetic mineral assemblages in freshwater and marine sediments is important for identifying and interpreting the magnetic record of environmental change [ Oldfield, 1992; Reynolds and King, this issue].
Instead of a general overview of biomineralization, I will highlight developments in the iron biomineralization of magnetic minerals by microorganisms made during the last quadrennium (1991-1994) that impact paleomagnetism, rock magnetism, and fine particle magnetism. For readers interested in more general aspects of biomineralization, several books and reviews have been published recently [ Lowenstam and Weiner, 1989; Mann et al., 1989; Frankel and Blakemore, 1990; Mann, 1993; Frankel and Mann, 1994]. The following discussion will briefly review four areas: magnetotactic bacteria, biomineralization, iron biominerals in sediments, and iron biominerals and fine particle magnetism.