Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Dkt. 73068/RDK
IMPROVED ROUND CUT GEMSTONE
FIELD OF THE INVENTION
This invention relates to a round cut gemstone having improved light
reflecting and dispersing properties.
BACKGROUND OF THE INVENTION
Diamonds have particular characteristics that distinguish them among
precious gemstones, and make them the most sought after and expensive of
all gemstones. Although clear, diamonds when cut properly display brilliance
and fire, owing to the reflection, dispersion, and refraction of light that
impinges on their surfaces.
Brilliance includes internal brilliance, which is caused by light rays that
enter the top or crown (and table if the gemstone has one), and reflect off
the
base or pavilion facets and back out through the top or crown undispersed.
Dispersion, also referred to as fire, occurs when white light gets broken
up into its component spectral colors, in much the same way that a prism
resolves light into component spectral colors. Dispersion is maximized when
a ray of light is reflected totally from the base facets and strikes the crown
facets at the greatest possible angle. Dispersion also occurs when a
gemstone moves with respect to an observer.
Scintillation, a third characteristic, occurs when the stone, the light, or
the observer moves with respect to one another. Scintillation displays itself
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flashes of light, and the cut may increase or decrease the tendency of the
stone to cause scintillation.
Round brilliant cut gemstones, particularly clear or uncolored
diamonds, but also colored diamonds, rubies, sapphires, and emeralds tend
to display more of the foregoing attributes than other cuts, and tend to show
more brilliance than emerald, square, oval, and princess cuts.
The conventional round brilliant cut include 56 facets, including eight
upper girdle corner facets, eight star facets, sixteen upper girdle facets,
eight
pavilions (or lower corner facets), and sixteen lower girdle facets. While
such
stones emphasize brilliance and dispersion, it would be desirable to increase
these qualities, without sacrificing the overall beauty and desirability of
the
stone.
It is therefore an object of the present invention to provide an improved
round brilliant cut that enhances the fire and brilliance of the gemstone.
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SUMMARY OF THE INVENTION
This and other objects of the invention are achieved, and the
disadvantages of other gemstone cuts are overcome by providing an
improved round cut gemstone having an increased number of facets. In a first
embodiment, the invention provides an improved round cut gemstone,
comprising a girdle, a crown above the girdle, and a pavilion below the
girdle,
the crown located between the girdle and a substantially flat surface defining
a table, the crown having two steps including a first step from the girdle to
a
crown break and a second step from the crown break to the table, the crown
including eight first step top corner facets, eight second step top corner
facets,
eight star facets, and sixteen upper girdle facets. The pavilion has a
plurality
of bottom facets and a centrally located culet at the bottom of the pavilion.
The pavilion includes eight pavilion or lower corner facets, sixteen outside
lower girdle facets and sixteen lower inside girdle facets.
According to another embodiment of the invention, the invention
provides an improved round cut gemstone comprising a girdle, a crown above
the girdle extending to a substantially flat surface defining a table, and a
pavilion below the girdle, extending from the girdle to a substantially
centered
culet at the bottom of the pavilion. The crown includes a first step extending
from the girdle to a crown break and a second step extending from the crown
break to the table. The first step has eight first step top corner facets, and
eight star facets. The second step has eight second step top corner facets,
sixteen upper girdle facets, and eight upper center girdle facets. The lower
facets of the stone on the pavilion include eight pavilion facets, sixteen
lower
outside girdle facets, and sixteen lower inside girdle facets.
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BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the invention will become
apparent to those of ordinary skill in the art from the following detailed
description of the preferred embodiments, appended claims, and
accompanying drawings in which:
FIG. 1 is a side elevational view of a first preferred embodiment of a
gemstone in accordance with the present invention;
FIG. 2 is a top view of the gemstone in FIG. 1;
FIG. 3 is a bottom view of the gemstone in FIG. 1;
FIG. 4 is a side elevational view of a gemstone in accordance with another
preferred embodiment of the present invention;
FIG. 5 is a top view of the gemstone of FIG. 4; and
FIG. 6 is a bottom view of the gemstone of FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates a first preferred embodiment of a gemstone 100 in
accordance with the present invention. The gemstone 100 includes a girdle
102, a crown 104 above the girdle 102 and a pavilion 106 below the girdle
102. The pavilion 106 comes to a point at the centrally located culet 108 at
the bottom thereof. The crown 104 peaks at a substantially flat table 120.
The girdle 102 extends around the perimeter of the gemstone 100and
may also be called a girdle plane. In the preferred embodiment, the girdle
102 has at least some thickness and defines some facets, but any such
thickness is relatively small compared to the sizes of the facets on the crown
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104 and pavilion 106. In the preferred embodiment, the girdle 102 thickness
is preferably about 1-2.5% of the depth of the gemstone 100, when measured
from the top surface of the table 120 to the bottom edge of the culet 108. In
the preferred embodiment, the girdle thickness can be described as being
"very thin" to "slightly thick," terms known and understood to those skilled
in
the art.
Referring to FIG. 1, the top facets of the gemstone 100 are arrayed on
the crown 104, which has two steps 110, 112. There are two crown angles a,
b, which demarcate the steps of the crown 104. Angle a is the crown angle
between the girdle plane and the first step 110, and angle b is the crown
angle between the second step 112 and the crown break 124. In the
preferred embodiment, crown angle a has a value in the range of about
34.5°
to about 33°, and crown angle b has a value in the range of about
33° to
about 30°. The height of each step 110, 112 in the crown 104 should
preferably be approximately equal, although the upper or second step 110
can be somewhat thinner or thicker than the first or lower step 112.
The upper step 112 preferably contains sixteen facets, each
substantially triangle-shaped. As shown in FIGS. 1 and 2, the facets include
eight second step top corners 122, which are triangular bezels extending from
the crown break 124 to table 120. The second or upper step 112 also includes
eight star facets 114, which are triangular shaped facets extending from the
meeting point of the corner steps to the middle of the corner of the second
step 112.
The first or lower step of facets 110 preferably contains twenty-four
facets, eight first step top corner facets 126, extending from the girdle 102
to
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the crown break 124. The first or lower step 110 also includes sixteen upper
girdle facets 128, which are halves from the meeting points of the corner
steps to the middle of the first step of the corner.
As shown in FIG. 2, which shows a top plan view of the crown 104, the
table 120 is a flat surface at the apex of the crown 102. The table 120 is
substantially octagonal, its typical shape in a round, brilliant cut stone.
The
table percentage, which is the width of the table 120 as a percentage of the
width of the girdle 102, in the preferred embodiment is preferably in the
range
of about 55 to about 60 %.
FIGS. 1 and 3 show the lower facets or the pavilion 106 of the
gemstone 100. These include eight pavilion facets 130, which are lower
corners extending from the culet 108. The lower outside girdle facets 132,
which are halves from the middle of the pavilion facets on the girdle side
facets to 85% to 90% of the rib of the pavilion facets toward the culet 108.
The lower facets 106 also include sixteen lower inside girdle facets 134 that
extend as halves from the meeting points of the lower outside girdle 102 on
the girdle side facets to 30% to 40% of the rib of the outside girdle facets
toward the culet 108. The gemstone 100 of FIGS. 1 and 3 thus has eighty
facets, rather than the conventional fifty-six, to increase the dispersion,
brilliance, and reflection of the gemstones 100, preferably a clear, colorless
or
colored diamond.
FIGS. 4 through 6 illustrate another preferred embodiment of the
gemstone 200 of the present invention, having 88 facets. The gemstone 200
has a girdle 202, a table 220, a crown 204, containing the upper facets, and a
pavilion 216, containing the lower facets. The upper facets of the stone, as
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can be seen with reference to FIGS. 4 and 5, include eight first step top
corner facets 222 (bezels from the girdle 202 to the crown break 206) and
eight second step top corner facets 224 (bezels from the crown break 206 to
the table 220). The top facets also include eight star facets 226 (from the
meeting point of the corner steps to the middle of the second step corner).
Additionally, the crown 204 includes sixteen upper girdle facets 228 (halves
from the meeting points of the corner steps to the middle of the first step of
the corner), and eight upper center girdle facets 230 (facets from the girdle
side).
Referring to the lower portion or pavilion side of the gemstone 200,
shown in FIG. 6, the lower facets total forty in number divided as follows:
eight
pavilions 232 (lower corners), sixteen lower outside girdle facets 234 (halves
from the middle of the pavilions on the girdle side facets to 85-90% of the
rib
238 of the pavilions toward the culet 240). The lower facets further include
sixteen lower inside girdle facets 236 (halves from the middle of the lower
outside girdle on the girdle side facets to 40-50% of the rib 238 of the
outside
girdle facets towards the culet 240).
In either embodiment, the culet 108 or 240 can be a point, a line, or a
facet with some width and length. A culet range between "none" and "small,"
which will be understood to those skilled in the art. "None" means that the
culet has no shape, or is simply a point (or substantially a point). "Small"
means that the culet, if a line, has a small length relative to the rest of
the
gemstone, or if a facet, has a small size relative to other facets in the
gemstone.
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For either embodiment of the invention, the gemstone should
preferably have the following proportions:
The width of the table should preferably be about 55-60% of the overall
width of the stone, the diameter at the girdle. The crown should be about 14
17% of the height of the stone, measured from the top of the table to the
culet.
The girdle should be 1.0% to 2.4%, while the pavilion, which extends from the
lower edge of the girdle to the culet, should be about 42.5 to 44.5% of the
height. The height should range from about 57.5% to 63.9% of the width.
Angle a, formed by the intersection of vertices of the upper edge of the
girdle and the lower edge of the crown should range from about 33° to
34.5°.
Angle b, formed at the crown break ranges from 33° to 30°.
In the preferred embodiment, the stone can be any stone, precious,
semi-precious or otherwise. Examples of precious stones are diamonds,
emeralds, rubies and sapphires. The gemstone of the present invention is
believed to have great appeal as a diamond stone mounted to serve as a
solitaire diamond engagement ring. Of course, the gemstone can be used in
a wedding or other ring with other stones, or for a different article of
jewelry
such as for a necklace, bracelet or earring either alone or with other similar
or
different stones.
Although not essential to the preferred embodiment of the present
invention, a diamond according to a preferred embodiment would preferably
have other desirable characteristics such as color (range D-I), clarity (range
internally flawless (IF) - very slightly included (VS2), carat weight,
fluorescence (none-medium), polish (good-excellent) and symmetry (good-
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excellent). These grading standards, if present in the stone, will enhance its
appearance and its interaction with ambient light.
The embodiments of the present invention thus have eighty and eighty-
eight facets. The facet can be made using conventional cutting techniques. A
gemstone is selected for cutting after studying by the cutter and determining
that it is an appropriate candidate for a round brilliant gemstone cut. For
example, any significant imperfections noted in the stone must be located
such that they will be cut away, or will be located in a place where they will
not
significantly affect the overall grade and appearance of the stone. After
that,
the stone is cut to provide the crown, girdle, and pavilion having the
requisite
number of facets for either than eighty or eighty-eight facet embodiment.
Following that, the stone goes through the usual polishing and inspection
steps known to those in the art.
Although two preferred embodiments have been shown and described,
numerous variations and modifications will occur to those skilled in the art
without departing from the spirit and scope of the invention, which is not
limited to the preferred embodiments and is defined in the appended claims.
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