Abstract
A gemstone is provided that has an improved brilliance, especially at the crown portion of the gemstone. The gemstone has a crown angle that is less than an ideal cut round diamond and, preferably the crown angle is less than 27 degrees. By reducing the crown angle of the gemstone, light entering one end of the crown portion may exit the opposite end of the gemstone. In addition, reducing the crown angle reduces the mass necessary for the gemstone. As a result, the gemstone has a width or diameter that corresponds to a larger mass gemstone that is cut according to conventional ideal proportions.
Claims
1. A circular-cut gemstone comprising: a girdle having a top edge and a lower edge; a crown extending from the girdle's top edge at a crown angle less than 23 degrees so that a substantial portion of light entering one side of the crown exits an opposite side of the crown; and a pavilion extending downward from the girdle's bottom edge and having a pavilion angle the same as an ideal-cut-diamond.
2. A circular-cut gemstone as set forth in claim 1, wherein the crown angle is less than 19.
Description
DESCRIPTION OF THE DRAWINGS
(1) FIG. 1 illustrates an ideal round cut diamond having a crown angle of 34.5.
(2) FIG. 2A illustrates light reflecting through a round cut diamond that is deeper than the ideal round diamond cut proportions.
(3) FIG. 2B illustrates light reflecting through a round cut diamond that is shallower than the ideal round diamond cut proportions.
(4) FIG. 2C illustrates light reflecting through an ideal cut round diamond.
(5) FIG. 2D illustrates light reflecting through a gemstone having a crown angle less than that of an ideal round cut diamond in an embodiment of the present invention.
(6) FIG. 3A illustrates an ideal round cut diamond having a brilliant table and a darker crown.
(7) FIG. 3B illustrates a brilliancy distribution of a ideal round cut diamond showing the dark crown of the diamond.
(8) FIG. 4 illustrates a gemstone having a crown angle less than an ideal cut diamond in an embodiment of the present invention.
(9) FIG. 5 illustrates a gemstone having a negative crown angle in an embodiment of the present invention.
(10) FIG. 6A illustrates the facets of the crown and the pavilion of the gemstone having a crown angle less than an ideal cut round diamond in an embodiment of the present invention.
(11) FIG. 7 illustrates a top view of the gemstone of FIG. 6 in an embodiment of the present invention.
(12) FIG. 8A is a diagram for illustrative purposes of a gemstone in an embodiment of the present invention.
(13) FIG. 8B illustrates the difference in brilliance between an ideal cut gemstone and a gemstone in accordance with an embodiment of the present invention.
(14) FIG. 9A illustrates a gemstone having a constant width and reduced mass by reducing the crown angle of the gemstone in an embodiment of the present invention.
(15) FIG. 9B is a diagram for illustrating the effect reducing the crown angle has on the volume of a gemstone in an embodiment of the present invention.
(16) FIG. 9C is a chart illustrating the effect reducing the crown angle has on the volume of a gemstone in an embodiment of the present invention.
(17) FIG. 10 is a representation of a gemstone having increased brilliance at the crown in an embodiment of the present invention.
(18) FIG. 11 is a view of a pavilion of a gemstone in an embodiment of the present invention.
DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION
(19) The present invention relates to a gemstone and method for cutting a gemstone having improved brilliance. The present invention is applicable to any gemstone and should not be deemed as limited to any specific type, shape, or size gemstone. Although the description below may contain some specific discussion of round cut diamonds, it should be readily apparent to a person of ordinary skill in the art that the invention is applicable to any gemstone, including but not limited to natural, synthetic, faceted, precious and non-precious gemstones.
(20) Referring now to the drawings, and in particular FIGS. 4-7, a gemstone 40 is generally shown. In one embodiment, the gemstone 40 is a round cut diamond. The gemstone 40, as illustrated in FIG. 4, has a height H defined between a first end 42 and a second end 44. In addition, the gemstone 40 has a width W defined between a distal end 46 and a proximate end 48.
(21) A table 50 of the gemstone 40 is the outer surface of the diamond at or adjacent to the first end 42. The table 50 is the flat surface or facet of the gemstone 40 adjacent to the first end 42. In a preferred embodiment, the table 50 has a width W1 that is a portion or fraction of the total width W of the gemstone 40. In a round diamond, for example, the table 50 is preferably 50% to 70% of the width W of the diamond and ideally 53% to 60% of the total width W of the diamond. The table 50 of the gemstone 40 may be cut within a predetermine range to increase brilliance as will be appreciated by a person of ordinary skill in the art.
(22) The table 50 extends from a girdle 52 as illustrated in FIGS. 4 and 6A. The girdle 52 divides the upper portion of the gemstone 40 adjacent the first end 42 and the lower portion of the gemstone 40 adjacent the second end 44. The girdle 52 may have a thickness defined between a top edge 53a and a bottom edge 53b. The shape of the girdle 52 may correspond to the shape of the gemstone 40. In an embodiment, the gemstone 40 may be a round cut gemstone, and the girdle 52 may be substantially circular. The shape of the girdle 52 may be determined or may be the result of junctions of upper girdle facets 88 and lower girdle facets 58. The girdle 52 may be faceted, as illustrated in FIG. 6A, for example, with a slightly mountainous and valley-like facet shape.
(23) The table 50 may be substantially parallel to the girdle 52. In an embodiment, the table 50 may be located below the top edge 53a and/or the bottom edge 53b of the girdle 52. In an embodiment, the table 50 may be positioned between the top edge 53a and/or the bottom edge 53b of the girdle 52. The table 50 may also be positioned and/or located above the top edge 53a and the bottom edge 53b of the girdle 52.
(24) A pavilion 60 is a lower portion of the gemstone 40 that is located opposite the table 50. The pavilion 60 is generally defined between the second end 44 and the bottom edge 53b of the girdle 52 of the gemstone 40. The pavilion 60 may converge from the bottom edge 53b of the girdle 52 to a culet 62 at the second end 44. In such an embodiment, the pavilion 60 may converge at an angle .sub.1; that is less than 90, and in one embodiment is preferably 40.75 with respect to the bottom edge 53b of the girdle 52. The culet 62 may have an angle .sub.1 that is less than 180, and in an exemplary embodiment is 98.50.
(25) As illustrated in FIGS. 6A and 11, the pavilion 60 is divided by a keel line 70. The pavilion 60 may comprise a circumferential succession of facets, including but not limited to, the lower girdle facets 58, main pavilion facets 72, and a culet 62 if needed. In an embodiment, the gemstone 40 may have eight of the main pavilion facets 72 and sixteen of the lower girdle facets 58.
(26) A crown 80 is an upper portion of the gemstone 40 adjacent the first end 42 as shown in FIGS. 6A and 7. The crown 80 may converge from the girdle 52 and terminate at the table 50. In an embodiment, the table 50 extends from the girdle 52, such as from the top edge 53a of the girdle 52. The crown 80 may have a circumferential succession of facets, including but not limited to star facets 84, bezel facets 86 and upper girdle facets 88. For example, the crown 80 may have eight of the star facets 84, eight of the bezel facets 86, and sixteen of the upper girdle facets 88.
(27) The gemstone 40 may, in an embodiment, have thirty-two facets on the crown 53, a facet on the table 50, twenty-four facets on the pavilion 60. Accordingly, the gemstone 40, in such an embodiment, may have a total of fifty-seven facets. In one embodiment, the gemstone 40 may have fifty-eight facets where the additional facet is the culet 62.
(28) The culet 62 may be a faceted point at the second end of the gemstone 40. The pavilion 60 may converge and terminate at the culet 62. The pavilion 60 may diverge from the culet 62 and terminate at the girdle 52.
(29) FIGS. 6A and 7 illustrate additional facets, namely facet 100 and facet 102. The facet 100 may be located at any intersection of one of the star facets 84, one of the bezel facets 86, and one of the upper girdle facets 88. The facet 102 may be located at the intersection of two of the upper girdle facets 88 and/or the girdle 52. Any number of the facets 100 and the facets 102 may be provided as will be appreciated by one of ordinary skill in the art. The facets 100, 102 may be polished onto the gemstone 40 to increase scintillation or to balance the color of the gemstone 40.
(30) The crown 53 intersects the girdle 56 at a crown angle .sub.1. Unlike ideal cut diamonds where the crown angle is preferably 34.5 degrees, the crown angle .sub.1 of the present invention is less than 34.5 degrees. In a preferred embodiment, the crown angle .sub.1 is less than 27 degrees, and ideally the crown angle .sub.1 is less than 23 degrees.
(31) In an embodiment, the crown angle .sub.1 may be zero degrees or even less than zero degrees relative to the top edge 52a of the girdle 52 as illustrated in FIG. 5. In such an embodiment, the table 50 is located below the top edge 52a of the girdle 52. Depending on the crown angle .sub.1, the table 50 may be located below the lower edge 53b of the girdle 52. The table 50 may be, for example, inverted with respect to the girdle 52.
(32) Reducing the crown angle .sub.1 from the conventional ideal cut crown angle may cause a risk of chip damage to the girdle 52. As a result, the thickness of the girdle 52 may be increased to prevent risk of any damage to the girdle 52. Theoretically, the thickness of the girdle 52 has no significant effect on the brilliancy of the gemstone 40 observed from the table 50 of the gemstone 40. Accordingly, depending on the crown angle .sub.1 and other characteristics of the gemstone 40, the girdle 52 may be thicker than conventional ideal cut gemstones.
(33) Advantageously, the diameter or the width W of the gemstone 40 is maintained even if the crown angle .sub.1 is less than that of an ideal cut diamond as illustrated in FIG. 9A. To this end, the width W of the gemstone 40 may correspond to a larger gemstone than the actual weight of the gemstone 40. For example, FIG. 9A illustrates maintaining the width W of the gemstone 40 of a one carat gemstone while reducing the mass to a 0.9, 0.8 and 0.7 carat. The reduction in mass is the result of lowering the crown angle .sub.1 from the ideal cut angle to 27 to 17 to 9. As a result, the gemstone 40 appears to be larger than its carat weight.
(34) In addition, FIGS. 9B and 9C generally illustrate the effect reducing the crown angle .sub.1 has on the overall volume in another embodiment of a gemstone 200.
(35) In this embodiment, the overall volume V of the gemstone 200 is calculated by the following formula:
(36)
(37) As shown in FIG. 9B, the shaded area illustrates the volume V of the gemstone 200. For this illustration, the pavilion angle is maintained at 40.75, the culet angle is maintained at 98.5, and the table size WI is maintained at 50% of the total width W of the gemstone. Moreover, for simplification purposes and showing only relative differences, and for the purposes of this illustration only, the overall width W is maintained at 1 millimeter. Thus, for the purpose of this illustration, the only variable being adjusted is the crown angle .sub.1. FIG. 9C is a table showing the actual volume and change in volume resulting from reducing the crown angle .sub.1. In FIG. 9C, column .sub.1 is the crown angle in question; column V is the actual volume of the gemstone 200 having the crown angle .sub.1 in question, which is calculated in accordance with the previously discussed formula and parameters. Column Comp is the relative difference in volume V between a gemstone having the crown angle .sub.1 in question and an ideal cut gemstone having a crown angle of 34.5 (i.e., the gemstone shown in the first three columns of the first row). As will become apparent, decreasing the crown angle .sub.1 reduces the volume V of the gemstone 200. Nevertheless, the width W of the gemstone 200 and width WI of the table 250 may correspond to larger gemstone than the actual volume of the gemstone 200. As a result, the gemstone 200 may appear larger than its actual volume.
(38) By reducing the mass and volume of each of the gemstones 40, more gemstones or larger gemstones may be cut from a given rough gemstone. In addition, gemstone cutters may be able to produce relatively higher quality gemstones by focusing on the width W of the gemstone 40 rather than the carat weight of the gemstone 40. Therefore, the present invention allows improved usage of rough gemstone as well as producing less expensive and higher quality gemstones.
(39) Advantageously, changing the crown angle .sub.1 of the gemstone 40 improves the brilliance of the gemstone 40. FIG. 10 illustrates the improved brilliance of the gemstone 40 where the crown angle .sub.1 is less than 27. By reducing the crown angle .sub.1 to be less than the 34.5 of the ideal diamond cut, the gemstone 40 gains more brilliancy of the diamond by brightening the dark crown portion of the conventional ideal cut diamond. Reducing the crown angle .sub.1 guides light entering from one side of the crown 80 to the opposite side of the crown 80. For example, light may enter the crown 80, reflect at the bottom pavilion 60, and return to the opposite side of the crown 80. The ideal cut round diamond having the crown angle .sub.1 equal to 34.5 is unable to direct light from one side of the crown 80 to the opposite side of the crown 80 (hereinafter the CC light). FIG. 2D, for example, illustrates the gemstone 40 where the crown angle .sub.1 is less than 27 causing the gemstone 40 to emit the CC light. By contrast, FIG. 2C illustrates an ideal cut round diamond that is incapable of emitting the CC light. As a result, the ideal cut round diamond has darker crown regions.
(40) FIG. 8A illustrates an example of how increasing the brightness of the gemstone 40 at the crown 80 greatly enhances the overall brilliance of the gemstone 40. In FIG. 8A, the gemstone is a round cut gemstone having a radius of 2 millimeters and the table 50 is 50% of the total width W (diameter) of the gemstone 40. In such an example, the area of the table 50 and the crown 80 is r.sup.2, where the radius of the table 50 is 1 millimeter and the radius of the crown 80 is 2 millimeters. Accordingly, the area of the table 50 is approximately while the area of the crown 80 is approximately 4. Therefore, because the area of the crown 80 is at least three times the area of the table 50, increasing the brilliance of the crown 80 can cause the overall brilliance to increase significantly. FIG. 8B illustrates the significant difference in brilliance between an ideal cut gemstone 10 and an embodiment of the present gemstone 40. As is clearly visible, the light 105 emitted from the ideal cut gemstone 10 is significantly less than the light 105 emitted from the embodiment of the present gemstone 40.
(41) Reduction of the crown angle .sub.1 to, for example, less than 27 not only brightens the crown 80 but also improves color grading and improves clarity grading. The color of the gemstone 40 in the case of a diamond is a measure of the whiteness of the diamond. For example, a one carat diamond having a K color may improve to a G or H color grading based on the improved brilliance of the gemstone 40. The clarity of the gemstone 40 may be improved, especially in the grading region of VVS and VS as the smaller inclusions are masked by the strong excess light returning to the crown.
(42) The gemstone 40 cut according to the specifications also maintains the light emissions common to an ideal cut round diamond, namely the table to table light (hereinafter the TT light). Unlike an ideal cut diamond where only a portion of the light entering the crown is reflected towards the table (hereinafter the Ct light), in a gemstone 40 cut according to the specifications, light entering the crown 80 is reflected from the immediate pavilion 60, to the opposite pavilion 60 and is emitted from the opposite side of the crown 80. Thus, the TT light may enter from the table 50, reflect at the pavilion 60, and emit from the table 50; and, the crown-to-crown light (hereinafter the CC light) may enter from the crown 80, is then reflected at the pavilion 60, and is emitted from the other side of the crown 80.
(43) The invention has been described above and, obviously, modifications and alternations will occur to others upon a reading and understanding of this specification. The claims as follows are intended to include all modifications and alterations insofar as they come within the scope of the claims or the equivalent thereof.
