A long rectangular gemstone shape, somewhat similar in shape to a loaf of French bread, hence the name.
A ladies style watch (or movement) featuring a thin rectangular or oval shape.
The transparent acrylic material used on the bezel of early model GMT-Masters in 1954.
The governor or controller of a watch; it consists of a metal wheel, now commonly made of Invar, a special steel resistant to changes in dimension due to fluctuations of heat or humidity and usually is mounted with a hairspring also of Invar or a similar alloy.
Also referred to as the “hair spring,” this spring controls the swing of the balance.
A portion of the escapement, which divides time into equal sections.
A diamond setting style that holds each diamond in by a thin bar, shared between the two diamonds.
Barion Cut Diamond
This has a traditional step-cut crown and a modified brilliant-cut pavilion. This is referred to as a mixed cutting style. A square Barion Cut diamond has 61 facets, excluding the culet.
The finish on some bracelet links that resembles the bark of a tree.
Irregular in shape, such as baroque pearls, tumble-polished stones, or freeform shaped gem materials.
Often called the “mainspring barrel,” this is a circular box, often connected to a gear, which holds the mainspring, which drives the watch.
A hollow gemstone, usually round, designed to be strung.
Tiny, numerous, hairlike fractures extending into the diamond. The outermost portion of the diamond, called the girdle, can develop small cracks that resemble whiskers during the shaping process. If a diamond is rounded up too quickly in the shaping process, the surface of the girdle will lack the smoothness and waxy luster of a finely turned girdle. The bearding can sometimes be removed, if not too dramatic, with slight re-polishing, and if the finished weight allows it.
Measured in either Beats Per Hour (BPH) or Beats Per Second (BPS). This is the number of times per hour or second that the balance wheel goes through a full arc of motion in either direction. The usual number of Beats Per Hour is 18,000. However, current Rolex watches are 28,800 BPH.
A form of heat treatment for sapphire that adds the element beryllium to the heating process. Beryllium is an element well known in the gem world, since it is an essential constituent in many gemstones, including emerald, beryl, and aquamarine. When sapphires are heated with beryllium, the result is a reduction in blue tones. Thus bright yellow or orange sapphire can be produced from weak yellow or greenish gems. Some stunning colors have been produced using this method.
The ring around the crystal on the top portion of a watch. Often, the bezel is made from varying materials (i.e. stainless steel or gold) within a watch line – See also Rotating Bezel, Bi-Directional Rotating Bezel and Uni-Directional Rotating Bezel.
On a Round Brilliant Cut diamond, these are eight large kite-shaped facets on the crown, the upper points of which touch the table and the lower points, touch the girdle. Also called top main facet. Some diamond cutters further distinguish four of these as “quoin” or “top-corner” facets.
A rim that holds the diamond and completely surrounds the diamond along the area just above the girdle. Bezels can have straight edges, scalloped edges, or can be molded into any shape to accommodate the diamond.
A gemstone exhibiting two color zones, such as ametrine or many tourmalines.
Bi-Directional Rotating Bezel
A bezel which can be rotated either clockwise or counterclockwise, and is used for making calculations.
Some gemstones are singly refractive they have only one refractive index. Other gemstones (in fact, most) are doubly refractive: they have two different refractive indices. When a beam of light enters a doubly refractive gem, it is split into two beams, each travelling at a different speed and on a different path through the crystal. Birefringence is a measurement of the difference between the two refractive indices in gems that are doubly refractive, and it ranges from a low of .003 to a high of .287. Very few gemstones are singly refractive; in fact, the only well-known gems with that property are diamond, spinel and garnet.
Birthstones have their roots in ancient astrology, and there have been many birthstone lists used over the years. The most common one today is based on a list first publicized by the U.S. jewelry industry in the 1950s.
When a diamond is dark gray, a very dark green, or truly black, it is referred to in the trade as a “black diamond”. Such a stone may be opaque to nearly semi-transparent.
Any surface imperfection on the surface of a diamond, such as a nick, knot, scratch, abrasion, minor crack or fissure (cavity), or a poor polish. Also, a natural or an extra facet, visible on or through the crown, usually is considered a blemish.
A diamond with a distinctly blue body color, even if it is very light in tone, is a fancy blue diamond. Boron that is present in the crystal structure is responsible for this color. A blue color may also be induced artificially and is referred to as a color enhanced diamond.
This is a term that I haven’t heard in many years… actually it was probably last century! It was still commonly used up till the mid 60′s. Federal Trade Commission rulings state that is it an unfair trade practice to apply the term to any diamond having a body color other than blue or bluish. An American Gem Society ruling prohibits the use of the term by its members. Flagrant misuse of this term has made it meaningless and it is no longer used.
A miner’s name for “kimberlite”, the rock that contains diamonds in the South African pipe mines.
The color of an unmounted diamond as observed when examined under a diffused light against a hueless (colorless) background free from
surrounding reflections. The diffused light eliminates glaring reflections and dispersion, which would otherwise confuse the color determination.
A diamond that has been subjected to a stream of fast electrons, neutrons, deuterons, etc. The purpose of bombardment is to alter the color of a diamond.
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. A large bow-tie in the center of a fancy shaped diamond detracts from beauty and lowers the value. (also ‘Butterfly’)
Boy’s size watch
2mm smaller than that of a standard men’s size watch.
Rolex Prince model with flared ends. From the French word meaning ‘stretcher.’
This is the term for the expansion and contraction of the hairspring. When breathing correctly, the spring is working at its optimum efficiency.
From the French word Brevette, meaning patented.
Any movement plate secured by a minimum of two screws.
The total amount of white light returned to the eye from a diamond or colored stone as the result of internal and external reflections. The major factors that affect the amount of brilliancy in a gem are refractive index, proportions, polish and transparency.
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, oval, radiant, princess, heart, marquise, and pear shape diamonds all fall within this category of faceting style.
The placing and polishing of the 40 remaining facets on a single cut diamond after the 8 main bezel, 8 pavilion main, and the table have been placed and polished. By adding the additional it is now called a “full cut” diamond.
A tear or pear-shaped stone cut in triangular facets.
Although not as frequently encountered as a yellow body color, brown tints in diamonds are next to yellow in occurrence.
Inclusions consisting of surface crumbling, often accompanied by tiny, root-like feathers .
Any transparent inclusion in a diamond; e.g., a tiny diamond crystal or a grain of a different mineral. It will look like a bubble.
Term used to describe the early Rolex Perpetual models, due to the thickness of the case used to house the oversized Auto-Rotor movement.
This facet may appear whitish, or burnt, as a result of the cutter polishing the facet “against the grain”. The excessive heat of polishing will make the diamond red hot and the surface will actually start to burn. This can also happened if the diamond is not properly protected from exposure to the atmosphere while being heating during repair work. A burnt facet can be re-polished.
Term used to describe the dark area located across a table, sometimes found in fancy shapes.