Ornamental diamond having two-stage pavilion

Abstract

An ornamental diamond is provided as an extremely bright diamond with numerous reflection patterns when viewed from above its table facet and crown facets. The diamond has the same crown as the round brilliant cut and its pavilion consists of a first pavilion and a second pavilion separated by a horizontal division plane. Lower girdle facets and pavilion main facets are bent by the horizontal division plane between the first and second pavilions, and a first pavilion angle is larger than a second pavilion angle. The ornamental diamond having the two-stage pavilion is much more brilliant than and has twice as many reflection patterns as the conventional round brilliant cut.

1 . A cut design of diamond comprising:
 a girdle of a round or polygonal shape having an upper horizontal section surrounded by an upper periphery and, a lower horizontal section surrounded by a lower periphery and being parallel to the upper horizontal section;   a crown of a substantially polygonal frustum formed above the upper horizontal section of the girdle and upward from the girdle, said crown having a table facet of a regular octagon which forms a top surface of the polygonal frustum; and   a pavilion of a substantially polygonal pyramid formed below the lower horizontal section of the girdle and downward from the girdle and having a bottom apex,   wherein, according to the following definition: a Z-axis is defined along a straight line extending from the bottom apex of the polygonal pyramid pavilion through a center of the table facet; first planes are defined as planes including the Z-axis and passing eight respective vertexes of the table facet; an X-axis is defined along a straight line passing a point where a first plane intersects with the girdle lower periphery, and being perpendicular to the Z-axis; a Y-axis is defined along a straight line passing a point where a first plane perpendicular to the Z-axis and the X-axis intersects with the girdle lower periphery, and being perpendicular to the Z-axis and the X-axis; and second planes are defined as planes each of which includes the Z-axis and bisects an angle between two adjacent first planes,   the crown has eight bezel facets, eight star facets, and sixteen upper girdle facets, as well as the table facet, each bezel facet is a quadrilateral plane whose opposite vertexes are a vertex of the table facet and a point where a first plane passing said vertex intersects with the girdle upper periphery, said quadrilateral plane has the other two opposite vertexes on respective adjacent second planes and shares a vertex out of the other two opposite vertexes with an adjacent bezel facet, each star facet is an isosceles triangle composed of the base of a side of the table facet and the vertex shared by two adjacent bezel facets whose vertexes are at the two ends of the base, and each upper girdle facet is a triangle composed of one side intersecting at one end with the girdle upper periphery, out of the sides of each bezel facet, and a point where a second plane passing the other end of said side intersects with the girdle upper periphery,   wherein the pavilion comprises a first pavilion and a second pavilion separated by a horizontal division plane parallel to the lower horizontal section of the girdle, the first pavilion has eight first pavilion main facets and sixteen first lower girdle facets, each first pavilion main facet is an isosceles triangle having the vertex at a point where a first plane intersects with the girdle lower periphery and having the base perpendicular to said first plane, on the horizontal division plane, each first lower girdle facet is a quadrilateral plane surrounded by a portion of the girdle lower periphery between a first plane and a second plane adjacent to each other, an oblique side of the isosceles triangle of the first pavilion main facet having the vertex on said first plane, a side on the second plane passing an end point on the second plane of said portion of the girdle lower periphery, and a side on the horizontal division plane passing a bottom vertex of the isosceles triangle, the second pavilion has eight second pavilion main facets and sixteen second lower girdle facets, each second pavilion main facet is a pentagonal plane having a vertex at the bottom apex of the pavilion and the base which is common to the base of the isosceles triangle of a first pavilion main facet, and being symmetric with respect to a first plane, said pentagonal plane has the other vertexes on respective adjacent second planes and shares one side and two vertexes with a second pavilion main facet adjacent thereto, and each second lower girdle facet is a triangle sharing a vertex of a second pavilion main facet present on a second plane, an end of the base of the second pavilion main facet, and a side of the second pavilion main facet having said vertex and end as ends thereof, with said second main facet, and composed of said side and a side of a first lower girdle facet on the horizontal division plane, and shares a side on the second plane with an adjacent second lower girdle facet,   wherein a first pavilion angle (p 1 ) between the first pavilion main facet and the lower horizontal section of the girdle is from 40° to 47°, wherein in a graph with the first pavilion angle (p 1 ) on the horizontal axis and a crown angle (c) between the bezel facet and the lower horizontal section of the girdle on the vertical axis, the crown angle (c) falls within a region between a straight line connecting two points where (p 1 , c) is (40, 27.8) and (47, 8.9) and a straight line connecting two points where (p 1 , c) is (40, 32.8) and (47, 15.0),   wherein in a graph with the first pavilion angle (p 1 ) on the horizontal axis and a second pavilion angle (p 2 ) between the second pavilion main facet and the lower horizontal section of the girdle on the vertical axis, the second pavilion angle (p 2 ) falls within a region between two straight lines, one connecting two points where (p 1 , p 2 ) is (40, 36.7) and (44, 37.0) and the other connecting two points where (p 1 , p 2 ) is (44, 37.0) and (47, 38.1), and a straight line connecting two points where (p 1 , p 2 ) is (40, 38.7) and (47, 41.3), and   wherein when an X-axis coordinate of a point where the girdle lower periphery intersects with the X-axis is 2.0, an X-axis coordinate (del) of a vertex of the regular octagon of the table facet present on the X-axis is from 0.9 to 1.2.