INTRINSIC CHARACTERISTICS

At the same time, the hardness is of such a nature that a diamond can chip when hit or struck by a door or an edge at the right place or angle. If it is struck by a hammer hard enough, moreover, it may and probably will shatter.

A diamond is hard. It is also brittle or fragile or frangible, synonyms sometimes used to describe this characteristic, which is related to cleavage. Some gems may simply be fragile and easily chipped or broken, but not in a particular pattern. In other gems, such as diamonds, the fragility results in cleavage.

Cleavage means that a gem has specific planes along which it will split, chip, or break. These planes can be likened to the grain in wood. A log of fireplace wood will split most easily when it is split with the grain. In the same way, a gem splits or cleaves most easily along its planes. Gem cutters use cleavage and cleavage planes to cut gems. Knowing that a certain gem is fragile or has high cleavage, therefore, will alert you to be more careful with that gem.

Toughness in gems is not a synonym for hardness. A tough gem is strong or firm in texture and not brittle. jade (see Chapter 4) is nowhere near as hard as diamonds. In comparison, nevertheless, it of the toughest-if not the toughest-stones known. Two -As struck together with force would be apt to shatter one another same force used with two pieces of jade would not ;e either piece. In short, diamonds are harder than jade and watch jade, but jade is tougher than diamonds because it is not and has no cleavage.

All hardness means, then, is that a hard gem will generally v less than a softer gem. Since it can also be more brittle, regardless of how hard a gem is, you should still use a little common n the "wear and tear" you give it. Despite this qualification, hardness is an intrinsic and desirable intrinsic in gems.