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A Edit 27 terms found

Abraded Culet
A culet that has minor abrasions on it.
Abrasion
Tiny nicks along facet edges, usually caused by contact with other diamonds. Producing white fuzzy lines instead of sharp crisp facet edges.
Acrylic Crystal
Also known as plastic crystals, these were initially introduced in the 1920s.
Adamantine
Refers to the diamond-like luster of a gemstone. Gemstones with a diamond-like luster include diamond (of course), demantoid garnet and sphene.
Age
The age of a diamond ranges between 1 billion to 3.3 billion years.
Alloy
Combination of 2 or more metals.
Alluvial Deposits
Gem deposits found in water after they have been separated from the mother rock.
Alluvial Diamond
A diamond that has been transported by water and deposited in seas, lakes or streambeds.
American Cut
Proportions and facet angles of a diamond that were mathematically calculated by Marcel Tolkowsky to produce maximum brilliancy consistent with a high degree of fire in a round brilliant cut diamond and are considered by many to constitute the “Ideal Cut” diamond. These figures, computed as a percentage of the girdle diameter, are as follows: total depth of 59.3% (without provision for girdle thickness); crown height of 16.2% (table 53% and Crown angle of 34.5 degrees); pavilion depth of 43.1% (pavilion angle of 40.5 degrees).
American Gem Society (AGS)
The American Gem Society was established in 1934 by a select group of independent jewelers and Robert M. Shipley, founder of the prestigious school of gemology, the Gemological Institute of America (GIA). It was their vision to create an association dedicated to setting and maintaining the highest possible standards of business ethics and professionalism in the jewelry industry. Today, American Gem Society members continue their dedication to ethics, knowledge and consumer protection.
American Gem Society Laboratory (AGSL)
Since 1996, the AGS Laboratories is the world’s premier diamond grading laboratory and the only diamond grading laboratory backed by the jewelry industry’s premier consumer protection agency, the American Gem Society, and the first prominent diamond grading laboratory to offer diamond grading reports with a Diamond Cut Grade for the round brilliant cut diamonds, princess cut, oval brilliant, and emerald cut diamonds.
American Gem Trade Association (AGTA)
The American Gem Trade Association and its members are active in all areas, from mines and research labs to wholesale offices, design studios and retail showrooms. As a result, the AGTA is recognized as the voice of the natural colored gemstone and cultured pearl industries. Some of the most significant contributions to the trade have been the creation of the AGTA Code of Ethics and Principles of Fair Business Practices, the Gemstone Enhancement Manual (G.E.M.), along with the opening of the AGTA Gemological Testing Center in New York in October 1998.
Amorphous
Gemstones without a crystal structure are referred to as amorphous. These include gems such as amber, coral, opal and pearl.
Anneal
A treatment process of heating and slow cooling of colored gemstones, color enhanced diamonds, and metals.
Aperture
Some watches contain small openings on the dials, called apertures, that show indications (i.e. numbered date, hour or day of the week).
Appraisal
A written estimate of the value of the item described. They can be used for insurance purposes and should be updated every few years.
Arabic Numerals
The figures on the dial that represent the hours, such as 1,2,3,4, as opposed to Roman Numerals I, II, III, IV.
Arbor
The shaft or axle that a gear rides on. At each end is a narrower segment called the “pivot.”
Arkansas Diamond
An Arkansas diamond is actually a rock Quartz crystal.
Art Deco
Art Deco was a style popular from the mid-1910′s until the late-1920′s. This style originated in Paris, France. Geometric lines and angles, with very few curves, characterize Art Deco pieces. The Asscher Cut diamond and the Emerald Cut diamond were developed and became popular during this period.
Asscher Cut Diamond
A square step cut diamond named after its inventor, Joseph Asscher.
Asscher, Joseph
Joseph Asscher was an eminent diamond cutter who cut the 3,106 carat Cullinan diamond. Asscher worked in Amsterdam. In 1902, his company, the Asscher Diamond Co., developed and patented the Asscher cut, a squarish step cut with an almost octagonal outline. This new cut enhanced the fire and light of the stone; it had a small table, a high crown, wide step facets, a deep pavilion and square culet. This cut became very popular in Art Deco jewelry and was a forerunner of the Emerald Cut diamond.
Asterism
The star effect that you see in star sapphires or rubies, for example. This is usually caused by tiny silk rutile inclusions in the stone. The effect can be four- or six- rayed.
Atmosphere
Used as a measure of the watertightness of a watch case. One atmosphere equals average air pressure at sea level, approximately 14.7 pounds per square inch. Since one atmosphere equals 33.90 feet of water, a 3 ATM water resistant watch is considered water resistant to approximately 100 feet.
Auto Rotor
Rolex patented perpetual movement invented by Emil Borer in 1931
Automatic Winding (also Self Winding)
An automatic watch is wound by the movement of the wearer’s wrist. This movement causes a weight inside the watch to rotate backwards and forwards. The weight is connected by a gear train to the barrel arbor, which is hooked to the mainspring, thus winding it and keeping it in constant tension.
Average Girdle Diameter
The average measurement of the minimum and maximum diameter of a Round Brilliant Cut diamond.