The chemical processes taking place in the crust are especially important as they have build ores, concentrated mineral deposits that are exploited industrially as sources of specific components and their elements. Summarizes the principal chemical forms in which each element perform. At least half the elements prepare in the crust as oxides (mostly complex ones such as silicates) or less commonly as halides, and are called lithophiles. All the bigger electropositive metals are in this class. Chalcophiles are components present in sulfide minerals; these include some elements chemically same to sulfur (As, Se) together with less electropositive metals of the later post transition and transition metal groups.
Fig. 1. The periodic table showing the principal types of chemical compound occurring for elements at the Earth's surface.