Throughout the centuries, humans have cherished the color and gleam of finished gems. Mineral crystals brought up from the dark depths of the earth, organic gems created by life processes—all gems worthy of the name share the virtue of beauty.

But because beauty is in the eye of the beholder, it isn’t always easy to categorize what’s beautiful and what isn’t. One accepted definition of beauty holds that it’s a combination of qualities that delight the senses or appeal to the mind. In other words, a thing of beauty might not cause everybody to react the same way, but it will cause everybody to react—it will have visual appeal.

In fashioned gemstones, visual appeal typically results from a combination of color, symmetry, and surface appearance. Of these factors, color is usually the most important for colored stones. From the deep green of a fine emerald to the shifting colors in an opal, color is the first thing you notice about a colored stone. For this reason, it’s usually the first consideration when you’re selling colored stones.

Symmetry, the second factor, means balance and harmony of cut. A stone is most appealing when its shape and proportions are balanced, so certain cut details enhance a gem’s beauty. You’ll learn more about this in Assignment 3.

A gem’s surface appearance, or luster, also influences its appeal. Most gems are polished to a high luster. Pearls, which are not fashioned in the same way most other gems are, owe part of their beauty to luster, too.

In addition to these three factors, transparency often plays a role in a gem’s beauty. Transparency describes how light passes through an object. The more transparent an object, the more light passes through it. Many gems are transparent, including emerald, garnet, and tanzanite. Light can pass through them with little or no distortion.

Opaque materials are on the other end of the transparency scale. An opaque object, like a brick, a sheet of plywood, or a floor tile, lets no light through. Opaque colored stones include hematite and turquoise. Some gems, like opal, have varying degrees of transparency in a range from transparent to opaque.

Not all gemstones have the same combination of these elements: Jadeite can be opaque—and beautiful. On the other hand, a ruby owes a good deal of its beauty to the fact that it’s transparent.

You might like one gemstone more than any other, but remember that ultimately your customer’s choice is the most important. If you recognize that each colored stone has at least one strong element of beauty, and you learn to appreciate it, you’ll sell that stone more effectively.