When you walk into a jewelry store, the number and variety of diamonds will probably dazzle you—literally. So you should know what to expect when you visit a jeweler, and some things to look out for. With the right information, you can ask informed questions, make informed decisions and have confidence that your purchase will be a wise one.

Of the 4Cs —carat weight, cut, color and clarity, which together determine a diamond's value, cut is one of the most important considerations in selecting a diamond.

When you compare diamonds at the jeweler, consider this: How a stone is cut determines how light is refracted back out. This translates to the amount of fire and brilliance that radiates from the stone. A well cut diamond refracts nearly all the light entering it out of the top (crown) and sides, creating greater fire and more brilliance, so the diamond will have a wonderful sparkle. A poorly cut stone, on the other hand, won't be as beautiful or as valuable.

The term “cut” is often used to describe the shape of diamond. But this is inaccurate. Cut is actually the craftsmanship applied in cutting the facets of the stone. The artisan attempts to cut a diamond to make the best use of light. Princess cut diamonds, emerald cut diamonds , round diamonds, etc. are all diamond shapes. You'll also hear about the ideal cut diamond – but don't let a jeweler tell you ideal cut is the only beautifully cut stone.

When a diamond is cut to good proportions, light is refracted from one facet to another, then dispersed through the top of the diamond. When a diamond is cut too deep, some light escapes through the opposite side of the diamond. If the diamond is cut too shallow, light escapes through the bottom of the stone before it can be reflected.

A well cut diamond is a brilliant diamond. Even a large diamond with superior color can look dull and lifeless if it isn't cut for maximum brilliance. So when you're shopping for a diamond, remember: Diamond brilliance equates to beauty, and contributes heavily to a diamond's value.

How diamond brilliance is measured

Brilliant diamonds are eye-catching, sparkle gorgeously in candlelight and draw envious stares from other women in the room. So when you compare diamonds in a store, you'll want to look for those that seem to explode with light.

State-of-the-art technology and innovation have improved the art of diamond cutting. In fact, a diamond cut today can deliver measurably more brilliance than older diamonds of similar quality and grading.

Modern technology can also be applied to measuring one of a diamond's key attributes. Diamond brilliance is measured by Return of Light, which is the amount of light returned through the top of the diamond and directed at the beholder.

GemEx Systems Inc., an independent laboratory, has applied recent advances in optical technology to create a new device for measuring Return of Light. Known as the BrillianceScope™ , this device uses five lighting angles to precisely measure the light that enters the stone and is then returned back.

When you shop for a diamond, find out if the jeweler uses a BrillianceScope™. Having the brilliance of a stone scientifically measured can take a lot of the guesswork out of your diamond purchase. But in the end, it is what appears most brilliant to your eye that is most important. Your bride-to-be and friends will not be looking at the diamond through an instrument. Use technology and grading to be your guide – but make the final decision with your eyes.

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