Cut: The cut of a diamond determines its brilliance. There is no single measurement of a diamond that defines its cut, but rather a collection of measurements and observations that determine the relationship between a diamond's light performance, dimensions and finish. Most gemologists consider cut the most important diamond characteristic because even if a diamond has perfect color and clarity, a diamond with a poor cut will have dulled brilliance.

Color: Acting as a prism, a diamond can divide light into a spectrum of colors and reflect this light as colorful flashes called fire. Just as when looking through colored glass, color in a diamond will act as a filter, and will diminish the spectrum of color emitted. The less color in a diamond, the more colorful the fire, and the better the color grade.

Clarity: Diamonds that are absolutely clear are the most sought-after and therefore the most expensive. But many diamonds have inclusions - scratches, trace minerals or other tiny characteristics that can detract from the pure beauty of the diamond. The GIA and AGSL use a detailed system of rules and standards to summarize the number, location, size, and type of inclusions present in a diamond.

Carat Weight: Once you've determined what cut, color, and clarity grade you're looking for in a diamond, it's easy to determine the carat weight of diamond that will fit within your budget.

Tips to Choosing the Right Carat Weight For You....

To choose the best carat weight of diamond, consider her style, the size of her finger, the size of your setting, and your budget.

 If you have a set budget, explore all your options and you'll find that there is a wide range of diamond carat weights and qualities available in your price range.

If your recipient is very active or not used to wearing jewelry, she may find herself bumping or nicking her new ring. Consider a smaller size diamond or a setting that protects a larger diamond from getting knocked against doors and counters.

Also keep in mind that the smaller the finger, the larger the diamond will appear. A 1-carat diamond solitaire looks much larger on a size 4 finger than a size 8.

If you have already chosen a setting, make sure you choose a diamond to fit. Look for the diamond size specifications of your ring or ask your Blue Nile diamond and jewelry consultant what size diamond you should look for.

Finally, if a large carat weight is important to you, yet you're working within a budget, consider a diamond with a good cut, SI1–SI2 clarity, and an I or J color grade.