Scientists estimate that the human eye can distinguish some 1 million separate colors. That’s just where the trouble begins in grading colored gemstones. Most jewelers will never stock all of the roughly 100 colored gemstones available today, but they may keep 25 or so on hand at any one time. Grading these stones is similar to grading diamonds in that three of the “four Cs” apply. Yet the rich complexity of colored gems makes the task considerably more challenging. Of the four Cs – color, clarity, cut, and carat weight – the first three pertain to a gemstone’s overall beauty, rarity, and desirability. Carat weight factors into a gem’s price but not its grade. Color. This is by far the most important component of a colored gemstone. Some dealers believe color accounts for no less than half the gem’s value. Clarity and cut are still important, but the first impressio