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. The second pavilion is an octagonal pyramid and its side faces form second pavilion main facets. The first pavilion is a hexadecagonal frustum with a top face on the horizontal division plane and its side faces form first lower girdle facets. First pavilion main facets extend from the girdle and between the first lower girdle facets, into between the second pavilion main facets. 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.

Abstract: The color stone 1 is formed of a material with a refractive index n of 1.55 to 2.40, and is subjected to round brilliant-cutting. The pavilion angle p and the crown angle c satisfy the correlation of, ?A(n)×p+B(n)+K1?c??A(n)×p+B(n)+K2 where, A(n) is represented by A(n)=?1.122×n5+9.14×n4?26.752×n3+32.982×n2?12.842×n, B(n) is represented by B(n)=?22.323×n5+184.166×n4?527.616×n3+594.102×n2?128.68×n, K1 is represented by K1=+4, and K2 is represented by K2=?4.

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.

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. The second pavilion is an octagonal pyramid and its side faces form second pavilion main facets. The first pavilion is a hexadecagonal frustum with a top face on the horizontal division plane and its side faces form first lower girdle facets. First pavilion main facets extend from the girdle and between the first lower girdle facets, into between the second pavilion main facets. 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.

Abstract: A cut design of an ornamental diamond and an observation method of the diamond which an observer can perceive a more beauty, are disclosed. The cut design is a round brilliant cut comprising a girdle, a crown above the girdle and a pavilion below the girdle. A girdle height (h) is 0.026 to 0.3 times a girdle radius, a pavilion angle (p) of a pavilion main facet ranges from 37.5 degrees to 41 degrees, and a crown angle (c) of a crown main facet is within a range of satisfying: c>?2.8667×p+134.233 and p<1/4×{(sin?1(1/n)+sin?1(1/n·sin c))×180/?+180·2c}, wherein n: refraction index of a diamond, ?: circular constant, p: pavilion angle in degrees, and c: crown angle in degrees. The cut design of the ornamental diamond provides an observer with plenty of visual-perceptible reflection when the observer watches the diamond above a table facet with a sight line of an angle less than 20 degrees with a vertical line at the center of the table facet.

Abstract: A cut design of an ornamental diamond and an observation method of the diamond which an observer can perceive a more beauty, are disclosed. The cut design is a round brilliant cut comprising a girdle, a crown above the girdle and a pavilion below the girdle. A girdle height (h) is 0.026 to 0.3 times a girdle radius, a pavilion angle (p) of a pavilion main facet ranges from 37.5 degrees to 41 degrees, and a crown angle (c) of a crown main facet is within a range of satisfying: c>?2.8667×p+134.233 and p<¼×{(sin?1(1/n)+sin?1(1/n·sin c))×180/?+180?2c}, wherein n: refraction index of a diamond, ?: circular constant, p: pavilion angle in degrees, and c: crown angle in degrees. The cut design of the ornamental diamond provides an observer with plenty of visual-perceptible reflection when the observer watches the diamond above a table facet with a sight line of an angle less than 20 degrees with a vertical line at the center of the table facet.

Abstract: When a diamond is brazed to a metal substrate, while obtaining a stable joining strength, a joined interface of the diamond is not eroded to provide a good joint with a beautiful view. A brazing-filler material containing at least one selected from a group consisting of gold and silver, and copper as principal components, and further containing 0.001 to 5 mass % of vanadium is used. Preferably, a vanadium content is not more than 2.0 mass %, and more preferably not more than 0.5 mass %. Using this brazing-filler material, unidirectional solidification is performed from a side of diamond to form vanadium carbide in a joined interface in a shape of islands, and thereby an interface having a beautiful view with stable joining strength can be obtained. In addition, strong joining is possible also by a usual solidification method.

Abstract: A diamond is provided which is subjected to an improved rectangular brilliant-cut producing a facet configuration having an optimal shape for the purpose of increasing the visual-perceptible reflection ray amount. In the rectangular brilliant-cut diamond, the bezel facets at the four crown vertexes each is bent along the diagonal line parallel to the girdle, to yield the facet configuration in which the bezel facet is divided into the lower bezel facet and the upper bezel facet. The upper crown angle of an upper bezel facet can be made smaller than the crown angle of a lower bezel facet, and hence even without altering the crown height, by making the table facet slightly smaller, the tilt angles from the horizontal of the star facets and the second bezel facets, both provided with intense reflection, can be made small and the areas thereof can be made large.

Abstract: A cut design for diamonds having a crown of substantially a frustum shape and substantially a conic pavilion directly under the frustum part, the diamond being enhanced in the brilliancy and scintillation of its crown part, the brilliancy and scintillation twinkling, and bluish lights being returned as reflected lights. A crown angle c and a pavilion angle p are so determined that lights coming in crown facets and emitted from crown facets, lights coming in the table facet and emitted from the crown facets, and lights coming in the crown facets and emitted from the table facet be directed toward the observer at the same time. Further, it is preferable to determine the crown angle c and the pavilion angle p so that the angles formed by incident lights and emitted lights are substantially equal to each other. Its table diameter should be between or equal to 0.60 and 0.33, more preferably not more than 0.55 and even more preferably not more than 0.38, in its ratio to the girdle diameter.