1. Cut

A facet is a flat, polished surface on a fashioned gemstone, and cut refers to the facet proportions on the surface of a diamond.

Brilliance, Dispersion Scintillation

According to dharamhk, the shape, placement and angle of each facet determines a diamond's brilliance, a quality which describes the intensity of the internal and external reflections of white light through the crown of a diamond. The ideal cut creates a diamond of perfect proportions, angles and finish, which cause it to reflect light like a mirror. In addition to brilliance, dispersion of light, and scintillation (the flashes of reflective light that emanate from a diamond when the diamond is moved, also called "sparkle") are also determined by a diamond's cut.

Sacrifice Diamond Size for Beauty

When a diamond is cut to maximize brilliance, dispersion, and scintillation, it usually loses size since more of the stone must be cut away. Likewise, when cut for maximum size, the diamond usually loses some of these beautiful qualities. The experts at  insist that it is best to choose a diamond for its beauty, not size, and that additional facets will not necessarily create a more brilliant diamond. A diamond's cut is considered the most important of the four C's, since this quality gives the diamond that irresistible shimmer and brightness that makes diamonds the king of all bling. Cut, therefore, has a major impact on the overall value of a diamond

2. Color

The ideal diamond engagement ring is colorless (white) or nearly colorless, the rarest of all diamond colors. The closer a diamond is to being colorless, the more valuable it will be. The Gemological Institute of America (G.I.A.) grades color alphabetically from D (totally colorless) to Z (yellow). For a diamond to be considered colorless, the G.I.A. requires that it be a D, E, or F - the average grade of diamond engagement rings in North America is G to H. The colored tint of most diamonds is the result of minute impurities within the stone; most of these tints are imperceptible to the untrained eye, however these invisible differences can affect the value of a diamond by thousands of dollars.

Fancy Diamonds

While most diamonds have a tint of color, a select few exhibit a strong, pure hue. Diamonds come in almost every color imaginable but the most popular colors are yellow, blue, green and pink. These colored diamonds are sometimes called fancies and are extremely rare, making them all the more sought-after.

3. Clarity

Even the most beautiful and valuable diamonds have natural imperfections called inclusions and blemishes. All gem-grade diamonds receive a clarity rating based on standardized industry scale: FL (flawless) to I3 (heavily included). Dharamhk say that a diamond is categorized as truly flawless if under the 10x power magnification of a loupe (a strong jewelry magnifying glass) no external imperfections and no internal flaws are visible. These unique specimens are exceptionally rare and therefore extremely expensive. Likewise, for those majority of diamonds which are not deemed flawless, the smaller and fewer the blemishes, the more valuable the stone. Many of the blemishes that reduce a diamond's value are invisible to the naked eye.

4. Carat

Carat is the standard unit of weight, not size, used for gemstones. One carat is equal to 0.200 grams. Large diamonds are very rare, and two diamonds of equal weight can have very different values depending on their clarity, color and cut.

Ethically Responsible Diamonds

While the diamond industry can bring essential jobs to hundreds of thousands of paid citizens and enormous economic value to many countries, the sale of blood or conflict diamonds has also funded brutal civil wars responsible for violence, slavery and atrocities in many African nations including Democratic Republic of Congo (formerZaire Sierra Leone and elsewhere. More consumers and retailers are exercising their political and ethical beliefs by choosing to purchase diamonds only from suppliers who certify that they are not endorsing bloodshed.