Patent ID: 7249471

Claim:
A method for displaying an ornamental diamond, the method comprising: providing an ornamental diamond of a round brilliant cut which comprises a substantially round or polygonal girdle having an upper horizontal section and a lower horizontal section parallel to the upper horizontal section, a crown on the upper horizontal section of the girdle having a table facet and at least one crown main facet, and a pavilion below the lower horizontal section of the girdle having at least one pavilion main facet, wherein a girdle height (h) between the upper and the lower horizontal sections of the girdle is 0.026 to 0.3 times a girdle radius, a pavilion angle (p) between the pavilion main facet and the lower horizontal section of the girdle ranges from 37.5 degrees to 41 degrees, and a crown angle (c) between the crown main facet and the upper horizontal section of the girdle is within a range of satisfying the following inequalities: c>− 2.8667 ×p+ 134.233 and p< 1/4×{(sin −1 (1 /n )+sin −1 (1 /n ·sin c ))×180/π+180−2 c} wherein n: refraction index of a diamond, π: circular constant, p: pavilion angle in degrees, and c: crown angle in degrees and displaying said ornamental diamond to establish a location of observation that is above the table facet of the diamond such that visually perceptible light coming into the diamond through the table facet and crown facets including the crown main facets, star facets and crown girdle facets is emitted from the table facet and the crown facets with a sight line having an angle less than 20 degrees with a vertical line at the center of the table facet.