The purpose of petrology is to understand the conditions of the formation of rocks. The first stage of this approach is to describe and classify the rocks; that is the subject of petrography. Many characters can be used: density, hardness, colour, structure (on the scale of the outcrop), texture (on the scale of the sample or of the microscope), mineralogical composition, chemical composition, speed of propagation of the waves, etc. Among all the characters, the mineralogical composition is certainly the most important: it allows us to, more or less, accurately foresee the other characters and it can be used to determine the very conditions of the formation of rocks. Indeed, the nature and chemical composition of the minerals in a rock obey stricter laws, since the formation temperature was higher

The shock metamorphic effects observed in meteorites can be described in terms of either deformation or transformation or some combination of the two. As mentioned in Chap. 3, the deformation effects include fracturing, plastic deformation, twinning, and mosaicism within constituent minerals. Planar deformation features (PDFs) have been attributed to deformational processes, but they have also been shown to contain transformed material, either diaplectic glass or high-pressure phases (Xie and Chao 1987; Goltrant et al. 1991; Bowden 2002).

Minerals, both metallic and nonmetallic, and building stones have played key role in shaping human civilization since ancient times. Demand for and production of these earth resources increased manifold during the Industrial Revolution and both have seen an exponential growth during the last century, keeping pace with growing national and global economies. Ever-widening base of mineral use has made minerals an integral part of our everyday life.