The present volume contains three independent publications dealing with the stability of heavy minerals. Two of these are concerned with experimental work on chemical (E. Nickel) and mechanical (V. Dietz) stability, which therefore are complementary to some extent. However, such laboratory experiments under earth surface conditions need verification by observation in natural occurrences. It was because of this that W.-D. Grimma was asked to contribute his previous and recent observations on one of the most spectacular German examples of surface weathering of heavy minerals to this volume.