Introduction

Summary

The physical and chemical properties of any part of the Earth depend critically on the particular assemblage of minerals that is present locally. Most of the minerals that are accessible to direct observation were formed at or near the Earth's surface, although some may have been brought up to the surface from deep levels in the crust or even from the upper mantle by processes such as volcanism and mountain building. Therefore, the minerals found at the Earth's surface may have formed over a range of temperatures from 0° to 1500°C and at pressures from 1 to more than 20,000 atmospheres. Every mineral or mineral assemblage contains within itself a record of its origin and of the physical conditions it has experienced since its formation. This record is, of course, far from perfect because later events in a rock's history often modify or obliterate the previously developed characteristics. Nevertheless, it is the physical and chemical characteristics of the minerals in the rocks exposed at or near the Earth's surface that constitute the most tangible link with the history of the Earth. Similarly, the minerals found in meteorites may contain information about the conditions that prevailed on the extraterrestrial bodies from which the meteorites originated. Thus, the study of minerals is one of the fundamental earth sciences and can be considered as the logical beginning of the science of geology.

Minerals are also important in another, perhaps more practical way.