Flexi Says: Many minerals and ionic compounds that are important to people take the form of crystals. Understanding crystal structures helps people identify minerals and ionic compounds. For example: calcium fluoride (CaF2)
has a cubic crystal structure. Crystal structure also helps scientists learn about the interactions of cations and anions in a crystal and to predict the properties of engineered materials. In biology, scientists study crystals of proteins and other complex organic molecules to learn about their structures and functions.