What is the primary structure of all garnets?

The primary structure of all garnets is classified as having a cubic crystal structure. This is significant because the cubic arrangement allows for the unique properties of garnets, including their characteristic crystal habit and symmetrical appearance. The cubic symmetry results in an isotropic optical property, meaning that garnets display the same optical characteristics in all directions, which can be particularly important when determining their quality and identifying different types of garnets.

This cubic structure underpins many of the physical properties that garnets possess, such as their refractive indices and cleavage patterns, making it a foundational aspect of garnet minerals. Other structures listed, like hexagonal and monoclinic, do not apply to garnets and reflect different crystallographic systems found in other minerals. While isomorphic structures typically refer to minerals with similar crystal structures, garnets are distinctly defined by their cubic geometry.