Final answer:
Two different minerals that share the same chemical formula but differ in crystal structures are called polymorphs, which is an example of polymorphism.
Step-by-step explanation:
When two different minerals have the same chemical formula but different crystal structures, they are said to be polymorphs.
This phenomenon is known as polymorphism, which is observed when a solid material exists in more than one form or crystal structure.
Examples of polymorphism can be found across various crystalline materials such as minerals, polymers, and metals. An example of polymorphism in minerals is the case of aragonite and calcite, where both have the same chemical composition of CaCO3 but exhibit different crystal structures.