It is now nearly 25 years since the first textbook on geostatistics ("Traitj de gjostatistique appliquje" by G. Matheron) appeared in print in 1962. In that time geostatis- tics has grown from an arcane theory regarded with scepticism by statisticians and miners alike, to a reputable scientific disci- pline which is routinely used in the geosciences. In the mining industry, in particularly, comparisons between predicted reserve estimates and actual production figures have proved its worth. Few now doubt its usefulness as a statistical tool in the earth sciences. Over the past quarter of a...