The sparkle of a well-cut diamond can actually make it appear larger than one might expect based on carat weight alone.
Cut is so important to a diamond's overall beauty, Blue Nile gemmologists recommend purchasing the highest cut grade within your budget.
All diamonds have varying degrees of brilliance, scintillation, and fire, but a well-cut diamond will always appear beautiful.
Poorly cut diamonds will appear dull or glassy, and, in those areas where light leaks out of the bottom of the diamond, may have dark areas.
Shape and cut are often used interchangeably, but while shape describes a diamond's form, such as round or oval, cut is a grade that refers to a diamond's light return, or, as we generally think of it, sparkle.
Diamonds with the highest cut grades cost more, not only because they are rarer, but also because of the skill and experience needed by the diamond cutter to produce such a beautiful stone. In addition, far more time is required to produce a well-cut stone.
The human eye tends to detect sparkle (light performance) before colour. This is why colour is generally considered the second-most important characteristic of buying a diamond, after cut.
As diamond size increases, colour becomes more noticeable. This is especially important to keep in mind if purchasing a diamond of two carats or greater.
The visible difference between diamonds of one colour grade, for example G to H or I to J, is so minor it is difficult to detect with the unaided eye. The cost savings, however, can be significant.
Diamond shapes that reflect more light (i.e. have more sparkle), such as round or princess, can mask some colour in a diamond.
The type of metal in which a diamond is set can complement its colour. Consider setting diamonds graded I or J in yellow gold. White gold or platinum best complement diamonds with a colour grade of D through H.
Most imperfections are so small they cannot be seen by the unaided eye.
If your budget is tight, it might be possible to purchase a diamond with a visible imperfection, but hide it beneath a ring claw where it will never be seen.
As diamond size increases, the size of the facets also increases. Because facets are essentially windows into a diamond, the importance of purchasing a diamond with a higher clarity grade increases.
Asscher- and emerald-shaped diamonds are designed with long facets that emphasise transparency over sparkle. For these diamonds, Blue Nile gemmologists recommend purchasing a diamond with a clarity grade of VS1 or better to ensure the imperfections will not be visible.
Carat weight alone will not give you an accurate view of a diamond's size, but should be considered in conjunction with the measure in millimeters across the top of a diamond, and the diamond's cut grade.
Diamond prices jump at the full-carat and half-carat marks. To get the best value, look for diamonds just below these sizes, for example purchase a .97-carat diamond instead of a one-carat. Visually, you will not be able to see a difference in size, but your savings can be significant.