Unravelling the enigmas of the ‘silver sands’ in the Dutch/German/Belgian border area

AbstractBright white sands consisting almost exclusively of quartz (sometimes called ‘silver sands’) occur throughout the world; those in Europe commonly date from the late Paleogene and early Neogene. They have a clearly sedimentary origin, and they may have originated in various types of environments, but precise data are lacking because sedimentary research into these deposits (that have a high economic value) has been scarce. It is most likely that diagenetic processes are largely responsible for their exceptional appearance, but it is highly unlikely that all silver sands were subject to the same diagenetic conditions.The precise origin of most of the silver sands is still enigmatic. In the case of the silver sands in the Dutch/German/Belgian border area, it appears that long-lasting in situ leaching by humic acids (resulting in an extremely low percentage of heavy minerals), in combination with differential cementation (and later partial dissolution of the cement), must be held responsible for the wide variety of the characteristics of these sands, including locally sharp boundaries with the underlying sands, lack of precipitates at the contact plane with the underlying sands, and the joint occurrence of strongly weathered and fresh specimens of the same heavy-mineral species.