Many natural resources renew themselves, but often do so much more slowly than they are extracted and used. This is true for oil, whose depletion may make the largely untapped oil shales a reasonable and economical source of energy in the future. Some resources can only be extracted at great cost or difficulty. For example, the mining of aluminum from its ore, bauxite, requires a great deal of energy, making the practice of recycling worth the effort.
Topic: Earth Science
Subtopic: Minerals and Resources
Keywords: Conservation of natural resources, Geology, Nature conservation, Mines and mineral resources