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L Edit 20 terms found

L
A grade in GIA’s Color Grading System…. in the middle of the “Faint Yellow” category.
Lab created
Refers to gemstones created in a laboratory rather than by nature. A lab created gemstone is typically the same material chemically as its natural counterpart, as in the case of corundum produced by flame fusion or quartz grown using the hydrothermal method.
Lady President
This nickname is often used to refer to the ladies ‘Rolex Datejust’ fitted with a President bracelet.
Lapidary
The science and art of cutting and polishing gems to their finished state.
Laser Cutting
Diamond has different directions that it can be cleaved, sawn, and polished. Using a laser to cut the diamond into an unusual shape is now possible. A laser can cut across the growth plains, which makes odd shapes such as letters, Christmas trees, tennis rackets, horse heads, etc. possible.
Laser Drill Hole
A hole is a tiny tunnel drilled into a diamond by a laser beam. The tunnel extends from the surface of a diamond down to a dark included crystal. The diamond is laser drilled in order to lighten a dark included crystal. After the diamond has been drilled the inclusion can be then bleached and become less noticeable. It might improve the clarity grade of the diamond but it usually will make a diamond much more marketable having a lightly colored inclusion verses a much more obvious darker inclusion. GIA’s Gem Trade Lab will issue a diamond grading report on diamonds that have laser drill holes (without any fracture filling) because the holes are permanent features and they will note the laser drill holes under the comments area of the report.
Laser Inscription
An extremely small inscription by a laser along the girdle of a diamond. This can be the diamond grading report number, a logo, a message, or a company’s name.
Length-to-Width Ratio
A ratio of how many times greater the length is in comparison to the width of a fancy shape diamond. Each fancy shape diamond has a range of ratios that are acceptable by most people. There is no “ideal” L to W ratio…. some are considered to be more appealing but it does turn out to be a personal preference.
Lever Escapement
Invented by Thomas Mudge in 1759. It subsequently replaced all other types of watch escapements, and is currently the only type of escapement manufactured for watches. Consisting of an escape wheel, “lever” and a balancing wheel, the lever, when initiated by the balance wheel, locks and unlocks the escape wheel, thus transferring power through the gear train in an even and controlled motion.
Leveridge Gauge
A commonly used device to measure the precise dimensions of a mounted or unmounted gemstones.
Light Yellow
A trade term used by some dealers to cover a wide range of colors in the low end of the diamond color-grading scale. Diamonds with a “touch of warmth”.
Ligne
A pre-metric system of measurement still used in Switzerland to measure watch movements. One ligne (“’) is approximately 2.256 mm.
Lively Stone
A diamond that has a reasonably good cut so that it has good brilliance and luster.
Lot
A large group of diamonds that have been closely matched in clarity, color, cut, and weight…. these diamonds are being offered for sale as an entire group and not piece by piece.
Loupe
A handheld magnifying glass used in the diamond trade to inspect diamonds. Magnification is usually 10X power and is corrected so as not to distort shapes and color. All diamonds are clarity graded under 10X.
Loupe Clean
When viewed under 10X magnification, a diamond is considered loupe clean if no obvious inclusions are immediately seen.
Lower Girdle Facets
These are triangular shaped facets, located on the pavilion just below the girdle.
Lugs
The two pointed edges on either end of the case, by which the bracelet is attached to the case through the end pieces. These are often called the ‘horns.’
Luminova
Organic, non-radioactive, luminous material now used on the hands and hour marker of a watch. It replaced the older (and more dangerous) radioactive material Tritium around 1998.
Luster
The quality and quantity of reflected light from the surface of a gemstone. Because of its hardness, diamond has an “adamantine luster”.