A dark area visible through the table in a stone with an inferior cut… the diamond is too deep.
Dark Included Crystal
An inclusion in a diamond which is dark in color. Many times, it is incorrectly referred to as a “carbon spot”.
DCI (Decompression Illness)
A condition, especially in divers, caused by the release of nitrogen bubbles in the tissue and blood upon too rapid a return from high pressure to atmospheric pressure —characterized by pains in the joints, cramps, paralysis and possibly death. This condition is often referred to as “the bends.”
De Beers and the various companies within the De Beers Family of Companies engage in exploration for diamonds, diamond mining, diamond trading and industrial diamond manufacture. De Beers is active in every category of industrial diamond mining: open-pit, underground, large-scale alluvial, coastal and deep sea. Mining takes place in Botswana, Namibia, South Africa and Canada.
A diamond so heavily included or so poorly cut that there is no brilliance (life).
Refers to the angles, symmetry, and proportions a diamond cutter uses in transforming a rough diamond into a faceted diamond. When a diamond is cut too deep, it will leak light through the side or bottom. This results in a diamond that is dark.
is a rare and valuable andradite garnet. It exhibits a range of greens from dull to bright emerald green and on rare occasions displays yellow. On Mohs scale of hardness, demantoid is relatively soft at 6.5. It has an adamantine luster.
The ratio of a gemstone when compared to the weight of an equal volume of water. This means how heavy a gemstone is compared to the same volume of water. Also known as “specific gravity” for solids.
The height of a diamond from the culet to the table. The depth is measured in millimeters.
On a diamond grading report, you will see two different measurements of the diamond’s depth- the actual depth in millimeters and the depth percentage (a percentage in relation to the diameter of a diamond). The (total) depth percentage of a diamond is the sum of the crown height, the girdle thickness, and the pavilion depth. It can give an indication of quality of the cut of the diamond.
This is the face of the watch, on which the hour markers (or indices) and hands are attached. On date and day-date models, an aperture is cut in the dial to allow the number wheels to be read.
The width of a round diamond… used as the reference point for the diamond’s proportions.
A form of crystalline carbon, made up of 99.95% pure carbon atoms arranged in an isometric, or cubic, crystal arrangement, singly refractive, a refractive index of 2.417, a dispersion index of 0.44, and a specific gravity of 3.52. It is by far the hardest of all known natural substances (10 on Mohs scale); only manmade Borazon and synthetic diamond are as hard. Now, that is a really romantic description of a diamond!
Also known as the Brilliant Cut, the style of cutting a stone with multiple facets to maximize brilliance. Modern round brilliant cuts have 58 facets.
A person engaged in the cutting and polishing of diamonds.
The process by which a rough diamond is transformed into a finished, faceted stone. As a first step, cleaving, sawing, or lasering is used to divide the rough into smaller, more workable pieces that will each eventually become an individual polished stone. Next, bruting grinds away the edges, providing the outline shape (for example, heart, oval or round) of the diamond. Faceting is next done in two steps:
An instrument that is used to measure a diamond’s length, width and depth in millimeters.
Diamond Grading Report
An expert opinion of the quality of a diamond, that contains information on identification, enhancements, carat weight, shape outline, measurements, color, clarity, and cut. Many include diagrams, top and bottom plotting diagrams of the diamond’s clarity characteristics. Usually issued by a disinterested 3rd.party, typically an independent gemological laboratory.
A saw used for sawing through diamonds as part of the diamond cutting process.
In the early days of South African diamond fields, the word “syndicate” was used to refer to various groups of individuals and companies that held controlling interests in diamond production and distribution. In 1890, a syndicate consisting of ten firms offered to produce all of De Beers Company’s diamonds: The term syndicate is no longer meaningful, it is often applied to De Beers Group, because it holds a controlling interesting in a number of diamond-mining companies and in companies that have buying contract with independent producers, including the Diamond Corporation, Ltd.
Diamond Trading Co., Ltd
The organization that markets to the diamond industry the gem diamond it buys from the Diamond Purchasing and Trading Co., Ltd.
A term meaning the ability of some gems to display a second shade of the same color when viewed from a different angle. A dichroscope can see this change, and is used for identifying certain stone.
The spreading of white light into its spectral colors. This typically occurs in the crown area of a diamond. Also referred to as fire.
Used on divers’ watches, a “hinged” extension within the watch’s bracelet allows the bracelet to be lengthened so as to fit over a wet suit.
One of the seven basic forms in the highest symmetry (“hexoctahedral”) class of the cubic, or isometric, crystal system. It has 12 rhomb-shaped faces, each of which intersects two of the crystallographic axes and is parallel to the third. This form is uncommon in gem diamonds. Did you understand that?
Double Named Watches (also Co-Branded)
Refers to watches that bear more than one company name on the dial (i.e. the manufacturer and retailer).
Double Quick Set
Introduced in late 1990, this feature allows both the day and the date to be rapidly set via the winding crown – See also Quick Set.
The ability of most gems to split rays of light into two rays.
A form of gemstone trickery that was devised to allow inexpensive materials to imitate the more valuable gemstones before modern synthetics were available. A doublet can take several forms but always involves a fake gemstone produced by gluing together two different materials to form an illusion.
A combination of hardness, toughness and stability that describes a specific gemstone’s ability to resist wear. The durability of a gem depends both on its hardness and “toughness”. It may be quite tough but easily scratched, or it may be exceedingly hard but lack toughness because of easy cleavage. Diamond is highest on the scale of hardness and, despite it rather easily developed octahedral cleavage, it is among the toughest of gemstones.