Dimorphism (crystallography)
Dimorphism is the property of some minerals to exist in two different crystal systems, while still having the same chemical formula. A common example is calcium carbonate, which exists as trigonal calcite or orthorhombic aragonite in nature. A mineral's dimorph is the mineral that it is dimorphic with. Dimorphism is not to be confused with allotropy, which refers to a difference in crystal structure of pure elements.Trimorphism & Polymorphism
Trimorphism is the term used when a mineral has a total of three dimorphs, while the term polymorphism is used when there are four or more. Silica, SiO2, is an example of this, being found in nature as quartz, tridymite, cristobalite, coesite, and stishovite. Pleomorphism is a synonym of polymorphism.
