Brilliant cut diamond

Details Brilliant cut diamond Brilliant cut diamond

2002-02-25

2004-03-02

Swann, J. J. (Department: 3677)

Jewelry

Gem

CD11S089000, CD11S090000

Reexamination Certificate

active

06698239

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to faceted gemstone construction and, specifically, to the faceted construction of a brilliant-cut diamond to provide improved luster and appearance.
2. Description of the Related Art
Because the present invention is primarily concerned with a brilliant-cut diamond (although the present invention may be applied to other gemstones), the discussion that follows will focus on brilliant-cut diamonds. The round brilliant cut sets the standard for all other diamond shapes, and accounts for more than 75% of diamonds sold today.
As shown in the prior art diamond profile of
FIG. 1
, there are three basic sections to a brilliant-cut diamond: the crown
110
, the girdle
120
, and the pavilion
130
. The girdle
120
is the narrow rim of the gemstone that separates the crown
110
from the pavilion
130
. It is the section with the largest diameter of any part of the stone. Usually it is left in an unpolished state with a matte finish. However, to achieve more overall brilliance (described below), girdle
120
is often ground. Crown
110
and pavilion
130
can be understood as the “top” and “bottom”, respectively, of the brilliant-cut diamond. The tiny facet on the pointed bottom of pavilion
130
is the culet
135
. The large, flat top facet of crown
110
is the table
115
.
For a cut diamond, a feature of primary importance is its brilliance, which is essentially how much it shines. A diamond has a refractive index of 2.42, which is a very high value compared with that of other jewels (the index of crystal is 1.55; rubies and sapphires, 1.77). As a result, when rays of light incident on table
115
reach pavilion
130
, most of the rays are reflected totally (i.e., the rays of light do not escape the diamond through pavilion
130
, but are reflected inward again), and escape upon reaching crown
110
, thereby reaching the observer's eyes as brilliance. The angle
137
of pavilion
130
is important to total reflection, and thusly is important to the brilliance of a diamond.
The refractive index of the diamond also gives rise to the dispersion of the totally reflected rays of light into the seven colors of the visible light spectrum. This rainbow effect is sometimes called the fire of the stone. Scintillation is the glittering of the reflected light of a diamond caused by the movement of either the observer or the diamond itself. Scintillation depends primarily on the size of the diamond, the number of facets, the polish of the facets, and the accuracy of the angles of the respective facets.
Diamonds are commonly assessed in terms of the “4 Cs”: Cut, Clarity, Color, and Carat. Cut refers to both the geometric proportions of a gemstone and the final form into which the rough stone is shaped. The most prominent cuts in the industry are the round brilliant, oval, marquise, pear, heart, emerald, princess, trilliant, and radiant. A good cut gives a diamond its brilliance, dispersion, and scintillation, in short, its appearance and appeal. Clarity is the measure by which a diamond is graded for purity, or whiteness. This is done by taking in the presence or absence of blemishes on the diamond's surface, or inclusions within the diamond. The professional grading scale is: flawless (F); internally flawless (IF); very, very slightly included (VV); very slightly included (VS); slightly included (SI); imperfect (I).
Color refers to the system of grading diamonds on the quality of their tint, from colorless to a pronounced yellow hue. Modern methods use letters to designate differences in colors. They are D-F, for colorless; G-J, for nearly colorless; K-M, for faintly yellow; N-R, for very light yellow; S-X, for light yellow; Y-Z, for yellow. The traditional method ascribes names to the variations in tint: pure white (extra river; river), top-white (wesselton), off-white (silver cape, tope cape, cape, dark cape), yellow, and brown. Carat is the unit of weight (equal to 200 milligrams) by which a diamond or other gemstone is measured. The word is derived from the carob bean, whose consistent weight was historically used to measure gemstones.
The present invention is primarily directed to the brilliant-cut diamond. The round brilliant-cut diamond is characterized by many facets of different shapes and sizes. This maximizes a diamond's brilliance by minimizing the amount of light that can escape through pavilion
130
, as well as maximizing the scintillation effect of the crown by increasing and varying the reflective surfaces. The typical brilliant cut has 58 total facets and may fit the “Ideal Cut”, a range of proportions and angles that are maintained as a standard by the American Gem Society.
The origin of the number of facets (i.e., 58) found in a typical brilliant-cut diamond, and of the “Ideal Cut” standard may be found in the history of gemstone cutting. The art of cutting and polishing gemstones is very old, but a unified science and theory of facet proportion is relatively recent. Before the 1900's, the predecessors of the round brilliant-cut diamond, such as the European or Old Mine cut, varied widely in appearance. Because of the limitations of technology, these diamonds had very small tables, large culets, and short pavilion facets; but there was no single widely-recognized or agreed-upon standard of cutting them.
In 1919, diamond cutter Marcel Tolkowsky wrote a doctoral dissertation that essentially established the modern standard of a brilliant-cut diamond. Using only his own visual assessments of different variations of diamond cuts, Tolkowsky posited a theory of what cutting angles would produce the most proportionate balance of brilliance, scintillation, and dispersion in a gem-quality diamond. His measurements for achieving this balance were exact and strict. Fortuitously, improved cutting techniques and technology were being developed at the same time that finally allowed cutters to achieve more precise and stream-lined designs. Since that time, Tolkowsky's measurements have evolved into the looser “Ideal Cut” standard promulgated by the American Gem Society (AGS).
However, over time, other diamond cutters have found ways to increase the brilliance of the brilliant-cut diamond by exceeding the typical 58 facets. For example, Huisman et al. (U.S. Pat. No. 3,286,486) took the “conventional twenty-four facets” of the brilliant-cut diamond and tripled them to create a pavilion with seventy-two facets. The greatly increased number of facets in the pavilion and the different angles at which a great many of them are cut result in enhanced brilliance. Nevertheless, Huisman et al. left the girdle and crown to be “of any conventional size”. A later patent by the same inventors increased the number of facets of the girdle (Huisman et al. (U.S. Pat. No. 3,585,764)).
Other diamond cutters concentrated on other features besides brilliance. For example, Freiesleben (U.S. Pat. No. 5,657,647) reduces the number of crown facets in order to create large planar surfaces on the top of the diamond in order to “create an impression of calm and hardness”. One diamond cutter sought to create greater dispersion (and the capability of highlighting colors) by etching fine grooves (0.1 &mgr;m to 1,000 &mgr;m) into the planar surfaces of the facets (Nakama (U.S. Pat. No. 5,612,102)). Another diamond cutter sought greater scintillation by making the number of mid-level pavilion facets an odd number rather than the standard even number of facets (Elbe (U.S. Pat. No. 3,788,097).
Although these attempts have met with varying degrees of success, there is always the need for a new brilliant cut which uniquely maximizes and balances the features of brilliance, dispersion, and scintillation of a diamond. Furthermore, there is the need for a brilliant cut with an increased number of facets (in comparison to the typical brilliant cut) in order to increase the brilliance, dispersion, and scintillation of the diamond.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a new and unique

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