What's cool about the structure of these structures, is that they actually have a clear hierarchy or tier.
The simplest is a Cubic or Isometric crystalline structure. This means that it is a crystal category where the basic unit cell forms a perfect cube. Three axes of equal length and all axes meet at exact 90-degree right angles. It has the highest internal symmetry of all seven crystal systems.
Minerals in this system are optically isotropic, meaning light passes through them at the same speed in all directions.
Next you have Tetragonal. Tetragonal crystals are a category of crystalline solids defined by a rectangular prism shape with a square base and a vertical height that is either longer or shorter than the base.
