Trace elements in black and oil shales

Data on the abundance of trace elements in oil and black shales, as well as and the average concentrations of trace elements in these caustobioliths, are considered. In general, oil shales are enriched in Li, Be, B, Rb, Ta, and Se and depleted in Mo, Re, Ag, Au, V, Th, Cu, Hg (and, perhaps, W, As, and U) relative to black shales. Tentative values of minimal concentrations of trace elements oil shales are presented that make the integrated processing of shale organic matter economically viable to obtain by-product concentrates of valuable trace elements useful as feedstock for their recovery.