Rounded rectangular gemstone
A rounded rectangular gemstone which comprises a crown provided with a planar table, a pavilion whose facets converge at a cutlet being disposed below said crown, and a girdle extending from said crown to said pavilion, said girdle being substantially perpendicular to said table and assuming a rectangular shape when viewed thereabove and therebelow, wherein said crown and said pavilion have substantially circular cross-sections along a plane parallel to said table and the facets of said pavilion are arranged in rotational symmetry about said cutlet and in mirror symmetry about lines of symmetry passing through said cutlet and the midpoint of each side of said girdle and through said cutlet and each corner of said girdle.
The present invention relates to the field of gemstones. More particularly, the invention relates to a rounded rectangular gemstone exhibiting the brilliance and fire of a Brilliant cut gemstone.
BACKGROUND OF THE INVENTIONTwo commonly found crystalline structures of diamonds are the octahedron and dodecahedron. A diamond with an octahedral structure has eight triangular facets, or sides, such that each facet is equally spaced from the center. A diamond with a dodecahedral structure has twelve rhombic facets, such that each facet intersects two axes of symmetry, forming an equal spacing from the point of intersection, and perpendicular to a third axis of symmetry.
To properly utilize these crystalline structures and to minimize loss of material during diamond cutting (normally referred to as polishing), two corresponding diamond cuts are commonly used: the Round-Brilliant Cut and the Princess cut. The Round Brilliant Cut is the most popular cut, achieving a good balance of brilliance and dispersion as a result of its symmetrical shape, and is generally produced from a dodecahedron, which approaches a spherical shape; however a material loss of 40-50 percent results with this cut. Traditionally a Round Brilliant Cut is produced with 58 facets. A Princess cut, having a rectangular shape and resulting in a corresponding material loss of approximately 20 percent, is generally produced from a given octahedral rough diamond, while the Round Brilliant Cut is generally produced from a given dodecahedral rough diamond. Even though a Princess cut diamond has a much lower material loss than that of a Brilliant cut, the cost of a Princess cut diamond is not significantly lower since it is produced from an octahedral rough diamond. The cost of an octahedral rough diamond is much higher than of a dodecahedron, from which a Brilliant cut is produced.
Two important characteristics of a diamond when used as a gem are its brilliance and fire. External brilliance, or luster, refers to the amount of light that is reflected from the top of the diamond. Internal brilliance is determined by the light rays that enter the top (generally referred to as “crown”), and that are reflected from facets of the base (generally referred to as “pavilion”) and then are reflected again through the top (or through the so-called “table”, if provided) as undispersed light. Fire, also referred to as dispersion, occurs when white light is separated into its spectral colors so that the gem sparkles when properly cut.
Maximum brilliance occurs when a diamond is cut to enable maximum light return through the surface of the diamond. As shown in
Diamond appraisers rely on another attribute, in addition to those mentioned above, in order to determine the quality of the cut. Since the cross section of both the top and bottom portions of a Brilliant Cut diamond is round, the image of the table is reflected around the cutlet, within the bottom portion of the diamond. The table reflection is an indication of the depth of the pavilion. For example, at a pavilion depth of 48 percent, a black spot appears throughout the table, whereas at the ideal pavilion depth of 43 percent the table reflection appears as a spot encompassing one-third of the area of the table. It would be appreciated that the appearance of the table reflection occurs only with Brilliant Cut diamonds due to its radial symmetry.
There have been attempts to reproduce the dispersion and brilliant of Brilliance Cut diamonds without a corresponding high material loss. U.S. Pat. Nos. 4,020,649 and 4,555,916 to Grossbard disclose a step-cut diamond, usually referred to as an Emerald cut, whose facets are broad with flat planes resembling a flight of stairs, that exhibits improved brilliance. According to these patents a diamond is cut with a straight edged polygonal girdle, a crown having table and girdle breaks in addition to a table, a pyramidal base having girdle and cutlet breaks, and a cutlet. U.S. Pat. No. 5,970,744 to Greeff discloses a cut cornered mixed-cut square gemstone in which the crown and pavilion are substantially square with four equal sides and corners about one-third the length of the sides. The pavilion sides and corners are defined by eight rib lines which extend substantially continuously from the girdle to the cutlet. Although these patents attempt to achieve the good brilliance and dispersion of a Brilliant cut, the effect nevertheless does not duplicate that of the Brilliant cut. Furthermore, the prior art diamonds do not have radial symmetry, and therefore a table reflection does not appear.
All of the prior art described above have not yet provided satisfactory solutions to the problem of producing a diamond with the brilliance and dispersion of a Brilliant cut without a corresponding high material loss.
It is an object of the present invention to provide a diamond exhibiting the brilliance and dispersion of a Brilliant cut.
It is an additional object of the present invention to provide a diamond lacking the large material loss of a Brilliant cut.
It is an additional object of the present invention to provide a diamond in which a table reflection appears.
It is yet an additional object of the present invention to provide a cost-effective diamond that is produced from a dodecahedral rough diamond
Other objects and advantages of the invention will become apparent as the description proceeds.
SUMMARY OF THE INVENTIONThe present invention relates to a rounded rectangular gemstone comprising a crown provided with a planar table, a pavilion whose facets converge at a cutlet being disposed below said crown, and a girdle extending from said crown to said pavilion, said girdle being substantially perpendicular to said table and assuming a rectangular shape when viewed thereabove and therebelow, wherein said crown and said pavilion have substantially circular cross-sections along a plane parallel to said table and the facets of said pavilion are arranged in rotational symmetry about said cutlet and in mirror symmetry about lines of symmetry passing through said cutlet and the midpoint of each side of said girdle and through said cutlet and each corner of said girdle.
The pavilion comprises:
a) a plurality of pavilion facets the lower edge of each converging at the cutlet, said plurality of pavilion facets comprising kite-shaped pavilion facets and shortened pavilion facets, the vertex of each of said kite-shaped pavilion facets extending from the corresponding corner of the girdle, whereby each of said kite-shaped pavilion facets is interspersed between a pair of said shortened pavilion facets and each of said shortened pavilion facets is interspersed between a pair of said kite-shaped pavilion facets, said kite-shaped and shortened pavilion facets arranged in rotational symmetry about said cutlet;
b) a plurality of lower hexagon facets arranged in such a way that a pair of lower hexagon facets is disposed between each pair of adjacent pavilion facets, each of said pair of lower hexagon facets comprising a larger and smaller facet, whereby said plurality of lower hexagon facets is provided with mirror symmetry about lines of symmetry passing through said cutlet and the midpoint of each side of the girdle and through said cutlet and each corner of the girdle; and
c) a plurality of hexagon facets, one side being collinear with the girdle, four sides being collinear with corresponding lower hexagon facets, and the remaining side being collinear with the end of said shortened pavilion facet.
The hexagon pavilions are cut at an angle ranging from 52-60 degrees, each of the lower hexagon facets is cut at an angle ranging from 47-53 degrees, and each of the pavilion facets is cut at an angle ranging from 39-44 degrees, with respect to the table.
Preferably, each of the hexagon pavilions is cut at an angle of 55 degrees, each of the lower hexagon facets is cut at an angle of 50 degrees, and each of the pavilion facets is cut at an angle of 41 degrees, with respect to the table.
The maximum depth of each hexagon facet ranges from 25-30 percent, and preferably 27 percent, of the maximum girdle length and the minimum depth of each hexagon facet is 0 percent.
As referred to herein, unless otherwise stated, the term “percent” relates to the ratio of a given gemstone dimension to the maximum girdle length. The girdle length is measured along a plane parallel to the table.
The pavilion depth ranges from 72-83 percent, and preferably from 77-78 percent, of the maximum girdle length.
Preferably 8 pavilion facets are employed, 16 lower hexagon facets are employed and 4 hexagon facets are employed.
The crown comprises:
a) a plurality of triangular star facets, the long side of which is collinear with one side of the table;
b) a plurality of intermediate bezel facets, two sides of each of said intermediate bezel facets being collinear with the short side of two adjacent star facets and the remaining two sides converging to the midpoint of one side of the girdle;
c) a plurality of corner bezel facets, two short sides of each of said corner bezel facets being collinear with the short side of two adjacent star facets and the long sides converging to the corresponding corner of the girdle; and
d) a plurality of triangular upper girdle facets, the long side of each of said upper girdle facets being collinear with the girdle and one of the short sides being collinear with a short side of an adjacent upper girdle facets.
Each star facet is cut at angle ranging from 13-22 degrees, each intermediate and corner bezel facet is cut at an angle ranging from 27-40 degrees, and each upper girdle facet is cut at an angle ranging from 39-62 degrees, with respect to the table.
Preferably, each star facet is cut at an angle ranging from 15.0-19.5 degrees, each intermediate and corner bezel facet is cut at an angle ranging from 33.0-35.0 degrees and each upper girdle facet is cut at an angle ranging from 47-55 degrees with respect to the table.
The vertex of each corner bezel facet that abuts each corresponding girdle corner defines a circle whose center is the projection of the cutlet onto the table, thereby providing radial symmetry.
The vertex of each intermediate bezel facet that abuts the midpoint of the corresponding girdle side defines a circle whose center is the projection of the cutlet onto the table, thereby providing radial symmetry.
The structure of the gemstone according to the present invention, wherein each hexagon facet is not projected onto a corner bezel facet, precludes the appearance of any shadows.
The girdle has a non-uniform height. The minimum height of the girdle ranges from 1-5 percent and the maximum height of the girdle ranges from 10-20 percent. Each side of the girdle ranges from 86-94 degrees, and is preferably 90 degrees, with respect to the table.
The table size ranges from 53-63 percent, and preferably at 58 percent, of the maximum girdle length.
Preferably 8 star facets, 4 intermediate bezel facets, 4 corner bezel facets and 16 upper girdle facets are employed.
BRIEF DESCRIPTION OF THE DRAWINGSIn the drawings:
Before commencement of diamond polishing, in order to achieve the cut illustrated in
As seen more clearly in
The facets of crown 12, as well as those of pavilion 14, as will be described hereinafter, are cut in such a way so as to provide a round shape that has rotational symmetry with respect to cutlet 16, thereby enabling the appearance of table reflection 17. The cut of the crown results in a particular table size, defined as the ratio of the length T of table 15 to the length G of girdle 8, and in a particular crown angle ø (see
A bottom view of pavilion 14 is shown in
Crown 50 is comprised by girdle 52, table 55, eight star facets 21(a)-(h), eight bezel facets 56(a)-(d) and 58(a)-(d), and sixteen upper girdle facets 60(a),(b)-67(a),(b). Girdle 52, which assumes a rectangular shape when viewed above and below the diamond, and defines the boundary of crown 50, is perpendicularly disposed with respect to table 55. The table size, or ratio of table length T to maximum girdle length G (see
Corner bezel facets 56(a)-(d) are adapted to the configuration of a rectangular girdle on one hand and the requirement of radial symmetry on the other. As a result the two short sides of each bezel facet 56 are collinear with the short side of two adjacent star facets 21, while the long sides converge to a corresponding corner of girdle 52. The four vertices of the corresponding bezel facets 56 that abut each corner of the girdle define a circle whose center is the projection of cutlet 69 (
Two types of pavilion facets are provided: kite-shaped pavilion facets 90, 92, 94, 96 and shortened pavilion facets 91, 93, 95 97. Each pavilion facet is cut at angle ranging from 39-44 degrees, and preferably at an angle of 41 degrees, with respect to table 55 (
The vertex of each kite-shaped pavilion facet extends from a corresponding girdle corner 99 to cutlet 69, such that the four kite-shaped pavilion facets, as well as the four shortened pavilion facets, converge thereto. As shown in
In addition to its rotational symmetry, pavilion 70 is advantageously arranged with mirror symmetry. Without mirror symmetry, the light which is reflected from the pavilion would not be uniform, and one zone of the table may be darker than another zone, thus detracting from the resulting fire. Referring now to
Hexagon facet 72 is adapted to provide a rectangular girdle with a pavilion having rotational and mirror symmetry. One side of each hexagon facet 72 is collinear with girdle 52. Four sides are collinear with corresponding sides of four lower hexagon facets, respectively, and the remaining sixth side is collinear with end 98 of the corresponding shortened pavilion facet. Each hexagon facet is cut at an angle ranging from 52-60 degrees, and preferably at an angle of 55 degrees with respect to table 55 (
Girdle 52 is shown to have a non-uniform height, ranging from a minimum height at the lower vertex of corner bezel facet 56 to a maximum height at the lower vertex of intermediate vertex 58. Since each side of girdle 52 is substantially perpendicular, i.e. ranging from 86-94 degrees, and preferably 90 degrees, with respect to table 55, its vertical projection, as shown in
As can be appreciated from the above description, the present invention demonstrates a novel gemstone exhibiting the brilliance and fire of a Brilliant cut gemstone even though the girdle is rectangular, when viewed thereabove or therebelow. It has been surprisingly found that the material loss associated with the gemstone of the present invention ranges from 30-40 percent of a rough dodecahedron, in contrast to a Brilliant cut, which results in a material loss of 40-50 percent of a rough dodecahedron. Novel facets are employed to achieve rotational and mirror symmetry, while being adapted to the structural limitation of a rectangular girdle.
While some embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried into practice with many modifications, variations and adaptations, and with the use of numerous equivalents or alternative solutions that are within the scope of persons skilled in the art, without departing from the spirit of the invention or exceeding the scope of the claims.
Claims
1. A rounded rectangular gemstone comprising a crown provided with a planar table, a pavilion whose facets converge at a cutlet being disposed below said crown, and a girdle extending from said crown to said pavilion, said girdle being substantially perpendicular to said table and assuming a rectangular shape when viewed thereabove and therebelow, wherein said crown and said pavilion have substantially circular cross-sections along a plane parallel to said table and the facets of said pavilion are arranged in rotational symmetry about said cutlet and in mirror symmetry about lines of symmetry passing through said cutlet and the midpoint of each side of said girdle and through said cutlet and each corner of said girdle.
2. The gemstone of claim 1, wherein the pavilion comprises:
- a) a plurality of pavilion facets the lower edge of each converging at the cutlet, said plurality of pavilion facets comprising kite-shaped pavilion facets and shortened pavilion facets, the vertex of each of said kite-shaped pavilion facets extending from the corresponding corner of the girdle, whereby each of said kite-shaped pavilion facets is interspersed between a pair of said shortened pavilion facets and each of said shortened pavilion facets is interspersed between a pair of said kite-shaped pavilion facets, said kite-shaped and shortened pavilion facets arranged in rotational symmetry about said cutlet;
- b) a plurality of lower hexagon facets arranged in such a way that a pair of lower hexagon facets is disposed between each pair of adjacent pavilion facets, each of said pair of lower hexagon facets comprising a larger and smaller facet, whereby said plurality of lower hexagon facets is provided with mirror symmetry about lines of symmetry passing through said cutlet and the midpoint of each side of the girdle and through said cutlet and each corner of the girdle; and
- c) a plurality of hexagon facets, one side being collinear with the girdle, four sides being collinear with corresponding lower hexagon facets, and the remaining side being collinear with the end of said shortened pavilion facet.
3. The gemstone of claim 2, wherein each of the hexagon pavilions is cut an angle ranging from 52-60 degrees, each of the lower hexagon facets is cut an angle ranging from 47-53 degrees, and each of the pavilion facets is cut an angle ranging from 39-44 degrees, with respect to the table.
4. The gemstone of claim 3, wherein each of the hexagon pavilions is cut an angle of 55 degrees, each of the lower hexagon facets is cut an angle of 50 degrees, and each of the pavilion facets is cut an angle of 41 degrees, with respect to the table.
5. The gemstone of claim 2, wherein the maximum depth of each hexagon facet ranges from 25-30 percent of the maximum girdle length and the minimum depth of each hexagon facet is 0 percent.
6. The gemstone of claim 5, wherein the maximum depth of each hexagon facet is 27 percent of the maximum girdle length.
7. The gemstone of claim 2, wherein the pavilion depth ranges from 72-83 percent of the maximum girdle length.
8. The gemstone of claim 7, wherein the pavilion depth ranges from 77-78 percent of the maximum girdle length.
9. The gemstone of claim 2, wherein 8 pavilion facets are employed, 16 lower hexagon facets are employed and 4 hexagon facets are employed.
10. The gemstone of claim 2, wherein the crown comprises:
- a) a plurality of triangular star facets, the long side of which is collinear with one side of the table;
- b) a plurality of intermediate bezel facets, two sides of each of said intermediate bezel facets being collinear with the short side of two adjacent star facets and the remaining two sides converging to the midpoint of one side of the girdle;
- c) a plurality of corner bezel facets, two short sides of each of said corner bezel facets being collinear with the short side of two adjacent star facets and the long sides converging to the corresponding corner of the girdle; and
- d) a plurality of triangular upper girdle facets, the long side of each of said upper girdle facets being collinear with the girdle and one of the short sides being collinear with a short side of an adjacent upper girdle facets.
11. The gemstone of claim 10, wherein each star facet is cut at angle ranging from 13-22 degrees, each intermediate and corner bezel facet is cut at an angle ranging from 27-40 degrees, and each upper girdle facet is cut at an angle ranging from 39-62 degrees, with respect to the table.
12. The gemstone of claim 11, wherein each star facet is cut at an angle ranging from 15.0-19.5 degrees, each intermediate and corner bezel facet is cut at an angle ranging from 33.0-35.0 degrees and each upper girdle facet is cut at an angle ranging from 47-55 degrees with respect to the table.
13. The gemstone of claim 10, wherein the vertex of each corner bezel facet that abuts each corresponding girdle corner defines a circle whose center is the projection of the cutlet onto the table, thereby providing radial symmetry.
14. The gemstone of claim 10, wherein the vertex of each intermediate bezel facet that abuts the midpoint of the corresponding girdle side defines a circle whose center is the projection of the cutlet onto the table, thereby providing radial symmetry.
15. The gemstone of claim 10, wherein 8 star facets, 4 intermediate bezel facets, 4 corner bezel facets and 16 upper girdle facets are employed.
16. The gemstone of claim 10, wherein each hexagon facet is not projected onto a corner bezel facet.
17. The gemstone of claim 1, wherein the girdle has a non-uniform height, the minimum height thereof ranging from 1-5 percent of the maximum girdle length and the maximum height thereof ranging from 10-20 percent of the maximum girdle length.
18. The gemstone of claim 1, wherein each side of the girdle ranges from 86-94 degrees, with respect to the table.
19. The gemstone of claim 1, wherein the ratio of maximum girdle length to minimum girdle length, when measured on a plane parallel to the table, ranges from 1-5.
20. The gemstone of claim 1, wherein the table size ranges from 53-63 percent, and preferably at 58 percent, of the maximum girdle length.
Type: Application
Filed: Oct 16, 2002
Publication Date: Jun 2, 2005
Inventors: Michael Kedem (Petah Tiqwa), Eran Mutai (Yavne)
Application Number: 10/492,712