ARAT

This factor is relatively easy to understand—you drop a diamond on a scale and weigh it in metric carats. The actual weight of a diamond is tiny—a 1.00-carat diamond equals just two tenths of a gram, so it would take 100 carats to equal just one ounce! Because such small differences in weight translate into big differences in value, one carat has been divided into 100 separate parts, like a dollar. Diamonds are routinely cut into standard fraction sizes: ¼, ½, ¾, etc. The actual weights of these fractions may vary—a ¼ carat diamond may actually weigh 0.23 carats, or twenty-three one hundredths of a carat, expressed as 23 points.

The relationship between diamond value and carat weight is pretty easy to understand on the surface: larger diamonds are more rare than smaller diamonds; therefore they are worth more. But larger diamonds are so much more rare than smaller diamonds that their value increases exponentially—a one carat diamond costs significantly more than 2 times the amount of the same quality ½ carat.

When choosing a diamond, remember that size is just one factor. If you are fortunate enough to be able to choose the largest size and best quality diamond regardless of price, there won’t be a trade-off. For everyone else, however, there are two approaches: focus on size over quality or quality over size. In order to get the maximum size for a particular price range, the color, clarity, and cut of the diamond may fall into the lower ranges that affect its beauty. The opposite extreme would be to choose a diamond that is very fine, almost investment quality, but it might be much smaller than an equally beautiful diamond that is in the middle quality ranges. The ideal solution would be a balance of size and quality.

• Ancient civilizations used the seeds from the carob tree to weigh against gems. Because of their small size and uniform weight, they made the ideal standard. The word "carat" has its origins in that ancient practice.

• Diamonds lose approximately 40-60% of their rough weight when they are cut. Over 1 million rough diamonds must be mined before one is found that can be cut into a 1.00 carat finished diamond!