A crystal is a solid body, which has flat and well-formed faces, with straight edges and sharp vertices. In everyday life we are surrounded by crystals (the common salt that we use in the kitchen, sugar, those found in coins, in the bones of the body or in the materials used in construction).
Crystallography is the scientific discipline that studies the characteristics and properties of crystals.
The most important thing about a crystal is to know its structure, which determines what its physical or chemical properties are. In this sense, it must be taken into account that a crystal has a regular geometric shape.
Crystals and minerals
Interest in crystals originated through the study of minerals. The alchemists of the Middle Ages wondered why each mineral had a certain geometric structure. Medieval scientists could not answer these kinds of questions. It was in later centuries that the configuration of matter began to be understood. In this way, it was observed that crystalline matter existed with a periodic order. Crystallography responded to this observation and this discipline describes how crystalline matter is formed, what its structure is and how it is organized. In this way, a crystal can be understood as a homogeneous solid that has an internal ordering in its polyhedral morphology.
Differentiating crystal from mineral, and the role of mineralogy
By defining what a crystal is, it is already possible to understand what a mineral is, which is a crystalline solid of natural origin. It could be said that mineralogy would be the knowledge that studies the chemical composition, structure, origin and properties of each mineral from its crystalline composition.
Crystallography, an even greater step in analysis
Crystallography goes beyond mineralogy. In fact, nowadays people talk about the science of materials, whose objective is the creation of new materials applicable to new technologies and industry. Some examples of this science are highlighted in nanotechnology or semiconductivity.
The case for carbon
A concrete example would be the case of carbon. When carbon crystallizes into a certain structure, it forms a mineral, diamond (the hardest known mineral). If the carbon crystallizes in a different structure, it can form graphite (one of the least hard minerals known). Thus, both minerals are identical from a chemical point of view and it is their organizational form that makes them unique and different.
