A mineral is a naturally occurring combination of specific elements that are arranged in a particular repeating three-dimensional structure or lattice.1 The mineral halite is shown as an example in Figure 1.4. In this case, atoms of sodium (Na: purple) alternate with atoms of chlorine (Cl: green) in all three dimensions, and the angles between
the bonds are all 90°. Even in a tiny crystal, like the ones in your salt shaker, the lattices extend in all three directions for thousands of repetitions. Halite always has this composition and this structure.
