This meeting is centred on one element, silicon, but our aim is to cover a great
variety of the activities of silicon which are in one way or another linked to
biology. First among these are its links with human biochemistry and medicine.
At the end come the links between the minerals, mainly soils, and living
systems, including microbial and plant life (Fig. 1). We have, then, a difficult
mixture of chemistries to consider. On the one hand we must look at the solid
state/solution chemistry of the soil in which, at least to a first approximation,
organic matter plays no part, and on the other hand we must look at molecular
chemistry in life. The first paper, by Dr Farmer, outlines mineralholution
chemistry. To put silicon chemistry in the general context of biology I shall then
give an overview of this subject, from minerals through amorphous materials
to biological function, stressing particularly the differences between the silica
deposits in biology, biominerals, and the more crystalline minerals of the rocks
and soils. One striking feature is the intimate role of aluminium in geological
(soil) minerals and in natural waters, in contrast to its virtual absence from
biogenic opal. (These silica biominerals differ from manufactured ceramics
and amorphous glasses and the distinction is important.)