Final answer:
The statement about polymorphs having two identical structures with different compositions is false; polymorphs have the same chemical composition but differ in atomic arrangement and crystal structure.
Step-by-step explanation:
The statement that polymorphs are minerals that will have two identical mineral structures but different chemical compositions is false. Polymorphs are actually minerals that have the same chemical composition but differ in their internal atomic arrangement and crystal structure.
An example of this would be carbon, which can exist as both diamond and graphite. Both have the same chemical composition, which is pure carbon, but they have different crystal structures. Another example is the recrystallization of aragonite to calcite, where both minerals have the same chemical composition of CaCO3, but different crystal structures.