The research object of earth science is the whole earth, studying the material composition, movement or existence form of solid earth, and the conditions and processes of its formation and change. Crystallography and Mineralogy is the main course of earth science, and its teaching purpose is to understand and master the basic components of minerals (including moon rocks and meteorites at present) that constitute the earth's solid substances, and to understand and master their main internal and external properties, formation and application in human production and life. Because minerals are naturally occurring crystals, the understanding of their internal and external properties, formation, changes and uses will be based on crystallography theory. Therefore, we take crystallography as the dominant content of this course.

Crystallography is a natural science that takes crystals as the research object, and takes the formation and change of crystals, the geometric properties of crystal external morphology, internal structure, chemical composition, physical properties and their relationships as the research contents. It mainly includes the following branches:

-Geometrical crystallography, which studies the external geometry and regularity of crystals.

-crystallography, which studies the regularity and defects of particle arrangement in the internal structure of crystals.

-Crystallogenesis, which studies the process and mechanism of crystal germination, growth and change.

Crystal chemistry, studying the chemical composition, structure and relationship of crystals.

-Crystal physics, which studies the physical properties of crystals and their formation mechanism.

The discipline system of crystallography is developed on the basis of geometric crystallography, a branch of mineralogy, and its forming history has gone through about 300 years. Since the middle of19th century, people have been exploring the internal structural characteristics of crystals, and at the end of19th century, they formed a mature geometric model, began to study synthetic crystals, and gradually merged with mathematics, physics, chemistry and other disciplines, thus breaking away from mineralogy and becoming an independent discipline with its own complete system. In the year of 19 12, the crystal structure was successfully determined by X-ray, which greatly promoted the rapid development of crystallography. Especially at the end of the 20th century, with the help of microbeam analysis technology and transmission electron microscope, human beings realized the dream of directly observing and analyzing the atomic arrangement and electronic state in crystals, which made crystallography enter a modern research stage characterized by micro-area and fineness.

As mentioned above, modern crystallography is characterized by its high integration with basic disciplines such as mathematics, physics and chemistry. Therefore, it is very necessary to learn mathematics and physics well and study crystallography deeply. In addition, because crystallography is the dominant course of mineralogy, it is also the important foundation of other geosciences related to mineralogy, such as petrology, mineral deposit science, gemmology, geochemistry, pedology, structural geology related to mineralogy, stratigraphy and paleontology related to the formation and change of geosciences, the interaction between geosciences and biology, and geophysics, life mineralogy and mineral pharmacy of crystalline substances in organisms. In the field of applied science and technology, many disciplines, such as mineral processing, metallurgy, metal and nonmetal materials, chemical technology and pharmacology, are closely related to crystallography. Therefore, crystallography is not only an important professional foundation of earth science and its extended disciplines, but also an important professional foundation of many other theoretical and technical sciences related to the national economy and people's livelihood.