Advanced Diamond Features

 A diamond’s polish is one of its most important advanced features. It refers to the smoothness of a diamond’s surface. Stones that have a polish grading of poor, very poor, or extremely poor, possess visible polish lines or granular texture along the facets.  Polish lines and graininess can give stones a blurry appearance, as they impede light performance, creating opaque stains where light is unable to pass through the diamond. These poorly polished stones loose their brilliance. When a diamond is graded, the level of polish is factored into the overall cut grade of the diamond. 

Diamond polish grades used by the Gemological Institute of America (GIA) are as follows:

A diamond’s symmetry refers to the proper alignment of its facets and the exactness of its shape. Symmetrical, well-aligned diamonds are the most brilliant and aesthetically pleasing. Defects in alignment include off-center tables, off-center culets, misshapen facets, and misalignment of crown or pavilion. A diamond’s symmetry flaws are usually hard to detect with the naked eye. Facets may have distorted shapes and the table may be warped. Symmetry flaws play a more significant role in diamonds with excellent clarity grades. It is always good to choose a diamond with Excellent, Very Good, or Good symmetry grades. However, diamonds with Excellent or Very Good symmetry grades are very rare. Stones with a symmetry grade of Good look striking, and it is hard to distinguish them from diamonds graded Excellent or Very Good for symmetry. 

Diamond symmetry grades used by the GIA are as follows:

 

Any material that emits a light glow when placed under ultra-violet lighting is fluorescent.  Many diamonds exhibit this characteristic when placed directly beneath UV light.  Fluorescent diamonds typically emit a light blue glow, but in roughly 1% of cases, they may glow in white, yellow, red or green.  Because ultra violet rays are also present in natural light, some diamonds may exhibit fluorescence in regular daylight. 

 

There is no clear consensus on the significance of a diamond’s fluorescence and its impact on a diamond’s value or quality.  Many believe that diamonds with a lower color grade (K-Z) appear whiter if they exhibit high levels of fluorescence.  There are subsequent claims that diamonds with a high color grade (D-J) appear milky or cloudy in color if they are very fluorescent.  You may find this manifest itself in diamond pricings, with D,E or F stones sold at lower prices when they exhibit high fluorescence, and K-Z stones sold at higher prices when they exhibit high fluorescence. 

Despite these claims, in 1997, the GIA published an extensive subject asserting that the impact of fluorescence on the appearance of a diamond is negligible. Therefore, while the fluorescence of a diamond may be evaluated and documented on a Diamond Grading Report, it does not impact the diamond’s color grade.  The GIA’s fluorescence grades are: Strong, Very Strong, Medium, Slight, and Faint.

If you are sensitive to color, we suggest that you do some window shopping of your own and develop your own personal taste regarding fluorescence. It is always important that you pick the diamond that meets your specific standards.

Fun Fact: Fluorescence is one method used to distinguish between real or synthetic diamonds such as moissanite or cubic zirconia. If a stone exhibits fluorescence when placed under ultra-violet light, it is almost positively a diamond. However, if a stone exhibits no fluorescence under UV light, it may still very well be a diamond, as not all diamonds exhibit fluorescence.   

A diamond’s brilliance refers to its brightness and its contrast. The cut of a diamond influences the way light reflects off its facets. If a diamond is too deep or too shallow, light will leak out of it, or their facets may act as mirrors and return less light. In order for a diamond too appear most brilliant, it needs to exhibit a certain degree of contrast between its various facets, much like a chess set. Contrast renders a diamond’s appearance brighter. The dark-bright alternating will make a diamond seem more brilliant, and will contribute to its scintillation (discussed bellow.)   

A diamond’s fire refers to its multicolored flashes of light, resembling a rainbow. These flashes are typically more visible in darker settings. They are more difficult to detect in broad daylight. Old cuts and certain fancy cuts featuring smaller tables usually exhibit more fire than today’s popular cuts, however the light return in these cuts is not as good. 

A diamond’s scintillation refers to the bright spots seen when a diamond is in motion. These sparkles are visible in flood lit environments where fire is usually less detectable. Fire may enhance scintillation under spot lights. Contrast will enhance a diamond’s sparkling appearance when the diamond is moved from side to side. Some leakage near the girdle might actually intensify a diamond’s scintillation. 

 

The anatomy of a diamond refers to the basic body-parts of a cut and polished diamond.  The way the parts of a diamond are aligned, proportioned, polished and shaped is what determines the quality of a diamond’s cut.  

Crown: The crown is the upper part of the diamond above the girdle.   It consists of the table, which lies flat, and the angled facets that surround the table. 

Table: The table is the largest facet.  It lies flat in the center of the face of the diamond. 

Star Facet: The star facet is shaped like a triangle and is the closest facet to the table. 

Bezel Facet: The bezel facet is shaped like a diamond with a long pavilion. It’s top tip touches the table, and the bottom tip touches the girdle. 

Upper Girdle Facets: The upper girdle facets are almost always cut in adjacent pairs and look a bit like sideways fangs.  They line the top of the girdle, or the bottom of the crown.

Girdle: The girdle is the belt or strip that runs around the middle of a diamond.  Some antique diamonds may not have a girdle. Today almost all diamonds are cut with a girdle since a well-cut girdle helps prevent chipping and cracking.  

Pavilion: The pavilion is the cone-shaped bottom section of the diamond.  It consists of the lower-girdle facets, pavilion facets, and typically includes a culet facet at the tip.

Lower-girdle facets: The lower-girdle facets line the bottom of the girdle, or the top of the pavilion.  They look like long fangs, or upside-down cones and are almost always cut in adjacent pairs. 

Pavilion facet: The pavilion facet is shaped like a long thin diamond and rises up from the bottom tip of the pavilion.  The bottom point of the pavilion facet touches the culet when there is one, and the top point of the pavilion facet touches the girdle.

Culet: The culet is a small, flat facet at the very bottom tip of the pavilion.  Not all diamonds are cut with a culet.