CULLINAN DIAMONDS GLOSSARY
Below please find the diamonds glossary terms from A - C
Abrasion: Abrasions are tiny nicks along the facet junctions, producing white fuzzy lines instead of sharp crisp facet edges.
American Gem Society (AGS): An educational institution for gemological studies. The AGS Labs were created primarily to develop and promote universally-accepted standards for grading cut.
AGS Cut Grading Scale
| 0 | Ideal |
| 1 | Excellent |
| 2 | Very Good |
| 3-4 | Good |
| 5-7 | Fair |
| 8-10 | Poor |
Appraisal: An Appraisal is a written estimate of the approximate retail replacement value of the item described. They can be used for insurance purposes and should be updated every few years.
Baguette: A step cut in the shape of a small rectangular stone. May be tapered at one end.
Bearded girdle: Tiny, numerous, hair like fractures extending into the stone.
Bezel:A facet on the Crown, or upper part of the Diamond above the Girdle.
Bezel Facet: On a round brilliant diamond, these are eight large kite-shaped facets on the crown. Also called top main facet.
Blemish: A clarity characteristic that occurs on the surface of a diamond. Though some blemishes are inherent to the original rough diamond, most are the result of the environment the diamond has encountered since it was unearthed.
Bort: Industrial grade diamonds Bow-Tie Effect: An effect caused by a shadowy area visible in some fancy shapes, caused by light leaking out the bottom of the Diamond.
Brilliance: The brightness that seems to come from the very heart of a diamond. It is the effect that makes diamonds unique among all other gemstones. While other gemstones also display brilliance, none have the power to equal the extent of diamond's light-reflecting power. Brilliance is created primarily when light enters through the table, reaches the pavilion facets, and is then reflected back out through the table, where the light is most visible to your eye.
Brilliant Cut: One of three styles of faceting arrangements. In this type of arrangement, all facets appear to radiate out from the center of the diamond toward its outer edges. It is called a brilliant cut because it is designed to maximize brilliance. Round diamonds, ovals, radiants, princesses, hearts, marquises, and pears all fall within this category of cut. BRILLIANT CUT DIAMOND Round diamond with 57 facets (58 if there is a culet). Round brilliant cut diamonds are more brilliant than any of the fancy-shaped stones.
The Cullinan Star CutTM diamond has an eight additional facets which adds more brilliance to the diamond.
Bruise: An inclusions consisting of surface crumbling, often accompanied by tiny, root like feathers.
Burned Facet: This facet may appear whitish, or burnt, as a result of the cutter polishing the facet "against the grain".
Carbon Spots: An inaccurate term used by some people in the jewelry industry to describe the appearance of certain inclusions in a diamond. The term refers to included crystals that have a dark appearance, rather than a white or transparent appearance, when viewed under a microscope. In most cases, these dark inclusions are not visible to the naked eye, and do not affect the brilliance of the diamond.
Carat: Diamonds are measured and weighed in carats with 1 carat representing .2 grams. The carat was traditionally measured against the carab seed, which were almost always the same size and weight allowing diamond traders to accurately evaluate their stock. As larger diamonds are mined less frequently, a 1 carat diamond will fetch a higher purchase price than two 0.5 carat diamonds provided all other characteristics are the same.
(Carat - see graphic to right)
Cavity: An inclusion consisting of a large or deep opening in the stone.
Chip: A tiny piece missing, caused by normal wear and tear, or by cutting.
Clarity: When diamonds are extracted, tiny traces of natural elements are sometimes caught inside, called inclusions. When polishing the diamond, the aim is always to reduce the number of flaws or impurities in the stone. The clarity inclusions fall into a number of categories: (Clarity - see graphic to right)
- IF – Internally flawless
- LC – Loupe clean meaning that there are no flaws in the surface or internally
- VVS 1 & 2 – Very, very small inclusion one and two has minute inclusions that are absolutely invisible to the naked eye and only through careful inspection with a microscope are revealed.
- VS 1 & 2 - Very small inclusion one and two may show tiny inclusions that are difficult to locate and are only visible to a trained eye looking through a 10x loupe can pinpoint the inclusions.
- S 1 & 2 – Small inclusions one and two are flaws that are easily identified through a 10x loupe.
- I1 & P1 – Lightly spotted are diamonds with inclusions that may or may not be visible to the naked eye.
- I2 & P2 - Spotted (no definition provided)
- I3 & P3 – Very spotted (no definition provided)
Clarity Enhancement: Any process used to improve the apparent clarity of a diamond. This may include filling fractures and cavities with glass/resin.
Cleavage: The propensity of crystalline minerals, such as diamond, to split in one or more directions either along or parallel to certain planes, when struck by a blow. Cleavage is one of the two methods used by diamond cutters to split rough diamond crystals in preparation for the cutting process (sawing is the other method).
Clouds: A grouping of a number of extremely tiny inclusions that are too small to be distinguishable from one another, even under magnification. The result is that, under a microscope, this grouping often looks like a soft transparent cloud inside the diamond. Of course, clouds cannot be seen with the naked eye. Usually, this sort of inclusion does not significantly impact a diamond's clarity grade.
Coated Diamond: A diamond colored by a surface coating which masks the true body-color; the coating may be extensive (entire pavilion, for example), but is more often limited to one or two pavilion facets or a spot on the girdle.
Colour: The colour of a diamond is graded from D to Z. The more colourless a stone, the more valuable it is. D, E and F represent truly colourless stones with the highest quality – making them considerably rare. Gradings from K to M have a slight hint of colour and as you go down the scale you’ll notice subtle colour changes in hue and tone. While the colourless stones are rare and valuable.
(Colour - see graphic to right)
Coloured Diamonds are even more exceptional. Called Fancy Diamonds, these stones are the most difficult to find and expensive to buy.
The Cullinan Diamond Mine is the most prominent source of fancy blue diamonds in the world.
Crown: The upper portion of a cut gemstone, which lies above the girdle. The crown consists of a table facet surrounded by either star and bezel facets (on round diamonds and most fancy cuts) or concentric rows of facets reaching from the table to the girdle (on emerald cuts and other step cuts).
Crown Angle: The angle at which a diamond's bezel facets (or, on emerald cuts, the row of concentric facets) intersect the girdle plane. This gentle slope of the facets that surround the table is what helps to create the dispersion, or fire, in a diamond. White light entering at the different angles in broken up into its spectral hues, creating a beautiful play of color inside the diamond. The crown angle also helps to enhance the brilliance of a diamond.
Crown Height: The part of the diamond that is above the girdle.
Crown Height Percentage: The crown height expressed as a percentage of the average girdle diameter.
Crystal: A type of inclusion. A crystal is a mineral deposit trapped inside the diamond.
Cut: This refers to the angle and proportion of the stone. Precision incisions allow maximum light to reflect off the facets. Imagine the facets are tiny mirrors bouncing light from angle to angle, beaming from the top and catching your eye. Cut to shallow, a diamond will lose its lustre. The Cut also includes the shape and weight of the diamond. A Round shape is considered the most brilliant shape of them all as it absorbs and reflects the most light, optimising the intensity of the stone.
(Cut - see graphic to right)
Culet: A tiny flat facet that diamond cutters sometimes add at the bottom of a diamond's pavilion. Its purpose is to protect the tip of the pavilion from being chipped or damaged. Once a diamond is set in jewelry, though, the setting itself generally provides the pavilion with sufficient protection from impact or wear. Large or extremely large culets were common in diamonds cut in the early part of this century, such as the Old European or Old Mine Cut. However, such large culets are rarely seen today. Most modern shapes have either no culet at all, or a small or very small culet.
