A hearts and arrows pattern is successfully generated from within a round cut diamond when exposed to light provided the round diamond was cut into a nearly perfect round shape possessing equal and symmetrically cut facets with its angular proportions satisfying relatively narrow ranges as taught below in Table I. The symmetry of a near perfect round cut diamond provides brilliance, color and optical light handling properties which, to date, no other shaped diamond has been able to match. Although diamonds are typically cut into many different geometrical shapes other than round such as, for example, a heart shape, oval, pear, marquis, princess, emerald, etc., only the round cut diamond has a nearly perfect symmetrical shape. For this reason, it was assumed, in the past, that a hearts and arrows pattern was a characteristic limited to the round shape and even then only when cut into a nearly perfect symmetrical shape with all facets of equal size and depth and cut at equal angle degrees. Contrary to conventional thinking the heart shaped diamond has a shape so irregular and non-round no one skilled in the art would have considered it possible to cut a heart shaped diamond and yield a hearts and arrows pattern when exposed to light.
In a round cut diamond the hearts and arrows pattern appears only when the requirements for its cut facets, angle parameters and alignment relationships are as shown in the following Table 1:
TABLE 1The shape of the diamond is perfectly symmetrical8 main crown and 24 subsidiary crown facets8 main bottom and 16 subsidiary bottom facetsAll main facets (crown & bottom) have to be polished at a perfect 45°angle to each otherAll facets are perfectly alignedAll the bottom main facets are of equal size and at an angle ranging from40.6°-41.0°All the bottom subsidiary facets are of equal size and at an angle which isexactly 1.2° steeper than the main facets (main bottom angle 40.6°-41.0° +subsidiary 41.8°-42.2°)All the main crown facets are of equal size and at an angle ranging from33.8°-35.1°. They have to be perfectly aligned on the main bottom facetsAll the subsidiary crown facets are of equal size and perfectly aligned onthe main crown and subsidiary bottom facets and polished at an equalangleThe ideal cut proportions are:total depth 59.4%-62.4%crown height 14.5%-16.0%girdle thickness 1.5%-2.95%Roundness 99.0%-100%Table size 53.0%-57.5%
USPTO Backgrounds
USPTO Backgrounds