As reflected in the table above, the world supply of oil appears heading for a disaster. These analysts marshal an impressive body of statistics to support their projections. Mineral deposits are usually divided into metallic and nonmetallic . If a mineral deposit is economically worthwhile to mine, then it is called an ore . A high grade ore consists of a high concentration of a valuable mineral in a localized volume of earth.
Underground mining involves tunneling into the earth and removing material.
Usually consists of mine shafts down to a horizontal layer of ore being removed. Placer mining usually involves the separation of valuable metals or nonmetals from unconsolidated material near the surface. Bauxite, the principle ore of aluminum, is often extracted this way. Igneous activity can produce high grade ores from fractionalization or magmatic segregation of magma chambers. Iron oxides have been found to solidify and settle towards the bottom of the chamber during cooling.