Final answer:
The Law of Crystallography states that the angles between equivalent faces of crystals of the same mineral are always the same.
Step-by-step explanation:
The law that states that the angles between equivalent faces of crystals of the same mineral are always the same is called the Law of Crystallography.
This law is based on the regularity of a crystal structure, which allows for the existence of multiple families of planes within its geometry.
Each family of planes gives rise to X-ray diffraction, which helps in identifying and analyzing crystals.