METHOD OF MANUFACTURING ROUND-SHAPED BRILLIANTS FROM DIAMONDS IN SHELL Russian patent published in 1997 - IPC

FIELD: diamond processing. SUBSTANCE: method includes examining, marking, and cutting diamond; preliminarily polishing, turning, and faceting stock. Preliminary polishing is two-step procedure, after the first polishing step, rough turning of fillet being additionally performed. In the first step, four bottom faces are polished along ribs of stocks at angle 45-90 deg. (advantageously 55- 60 deg.) with respect to site to achieve pure diamond body. Maximum dimensions of the latter are measured in each natural plane to be used as basis to determine tentative diameter of brilliant. Afterwards, polishing of bottom faces along stock ribs at angle 55-60 deg. is resumed to attain the distance from apex of each face through pure diamond to the site to be the value determined from equation: where D is tentative diameter of brilliant and α angle of slope of face to site. Four bottom faces are then polished using natural faces to attain their base size to be 0.5 tentative diameter of brilliant for stock constituting largest part of octahedral crystal of diamond and 0.6 for stock constituting half octahedral crystal or its minor part. Rough turning of fillet is fulfilled to attain its height on faces polished along stock ribs to be 0.08-0.12 tentative diameter of brilliant. In the second step, eight bottom and four to eight top faces of stock are polished, whereupon faces retaining rest of shell are polished to completely remove shell. EFFECT: reduced diamond loss. 3 dwg