Report of the Working Group on Placer Minerals

Abstract

Placer deposits are detrital sediments which contain potentially economic concentrations of valuable heavy minerals concentrated by hydraulic processes. Among the four types of marine mineral deposits that are the subject of this book, only placers are currently mined. Assessment of the resource potential of these deposits presents the same problems that are inherent to land-based placer deposits, namely, the diversity of placer types and the mineral commodities contained therein, the difficulty in defining a deposit, and the effects of the vagaries of mineral market conditions. Exploration and assessment in the marine realm, compared to onshore deposits, also presents a different set of problems because offshore deposits (1) are concealed by water as well as by solid material; (2) may not fit the genetic descriptions that are based on knowledge of onshore deposits; (3) are subjected to submarine processes that effect their alteration and preservation; and, (4) are in an environment that makes sampling more difficult and less precise than that on land.