Do old spoils contain large amounts of economically valuable minerals?

This paper focuses on the enormous losses of native gold and diamonds, during extraction from gravel deposits, using traditional methods of gravity concentration. Essentially, the density of a mineral influences its accumulation in nature, and, thus, the degree of extraction, using the technological process of gravity concentration. Data of diamond and gold extraction from important economic deposits in Russia, South Africa, South America, Mongolia as well as a prospective ore complex in Israel are analyzed. It is shown that, in heavy concentrates and middlings, fragmental (placer-generating) minerals, with different values of average density, may have similar or identical sizes. This factor may cause serious losses during exploitation.