Internal Structure of Gems

Internal Structure: The particular combining abilities of each kind of atom go a long way toward determining what combinations or compounds are possible. At the time a mineral forms, there are restrictions relating to the size, characteristics, and numbers of atoms present. Atoms are energetic, and exhibit this as rapid, erratic motion. As they rush about at phenomenal speeds they tend to fasten onto each other by strong attractive forces. Many trillions of atoms may pack themselves together this way in the course of an hour during the formation of one of these mineral solids.

This would suggest that they all end up in a great, unstable, chaotic mass. Instead, because of the uniform distribution of attractive forces and relatively uniform sizes, they line up in remarkably orderly, repetitious, geometric patterns and hold themselves quite tenaciously in these patterns called crystal lattices. A good demonstration of how this happens can be prepared by shaking up a basketful of tennis balls. They all quickly settle down into an orderly geometric stacking pattern as they come to rest against each other. Nature permits surprisingly few stacking patterns, and all solid mineral crystals prove to have their atoms arranged in one of fourteen basic patterns, or combinations of these patterns. In any such pattern a foreign atom or impurity atom would have to have nearly the same size and attractive power as the others in order to fit into the structure. Atoms too large or too small are rejected and cannot enter the combination. It is not unusual to see iron atoms substituting for manganese atoms in some structures and chromium substituting for aluminum in others. Each member of the pair is quite close to the other in size and attracting ability and is, therefore, not rejected by the structure.