Introduction

Mineral deposits, which supply society with most of its raw materials, are considered to be "nonrenewable" by most geologists because they do not form as rapidly as they are used. Thus, their production from Earth is not "sustainable" (Wellmer and Becker-Platen 2007). Most discussions recognize this fact by indicating time limits for mineral sustainability that range from a few generations to 200,000 years (NRC 1999b; Pickard 2008). Which end of this time range is more realistic for mineral resources depends in part on the stocks and flows of mineral resources in society, the characteristics of conventional mineral deposits that supply society, and the stock of conventional and unconventional mineral deposits that constitute Earth's ultimate mineral resource.

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