Stage 1: Marking and sawing
After planning, the rough is marked with ink to indicate the sawing or cleaving line. Modern sawing uses laser sawing, a focused laser beam that can cut along any desired plane, regardless of crystal orientation. Before laser technology (widely adopted in the 1970s onward), mechanical sawing used a phosphor bronze blade spinning at high speed, impregnated with diamond powder, requiring the blade to be precisely oriented to avoid the crystal's hard grain directions. Laser sawing has largely replaced mechanical sawing for most division operations because it is faster, more precise, and not subject to grain orientation constraints (GIA Diamond Grading documentation; historical cutting methodology).
Stage 2: Bruting (girdling)
Bruting creates the circular girdle of a round brilliant. Two diamonds are mounted on spinning spindles facing each other; rotating one against the other wears away the corners of both stones to create round girdles. Modern bruting uses a lathe-type setup where one stone spins on a horizontal axis while the other, the "bruiting" stone, is pressed against the equator of the spinning stone. The process shapes the girdle to the desired roundness before faceting begins. Fancy shapes (oval, pear, marquise) do not require bruting, their girdles are shaped during faceting (GIA Diamond Grading documentation; industry cutting methodology descriptions).
Stage 3: Blocking (placing the main facets)
Blocking establishes the stone's main facets, the table, culet, the eight main crown facets, and the eight main pavilion facets. The stone is mounted in a dop (a metal holder) on a tang (a mechanical arm) that controls the angle at which the stone is presented to the grinding wheel. The blocker grinds each main facet to the planned crown and pavilion angles, working to the specifications derived from the planning stage. For a round brilliant, blocking typically produces a 17- or 18-facet stone that establishes the proportions for the completed cut (GIA Diamond Grading documentation; industry cutting descriptions).
Stage 4: Brillianteering (adding the remaining facets)
Brillianteering adds the remaining facets to complete the round brilliant's 58-facet arrangement (or 57 if the culet is a point rather than a small facet). The brillianteer adds the upper and lower girdle facets (16 each), the star facets (8), and the kite facets (8), the facets that create the fire and scintillation pattern characteristic of the brilliant cut. This stage requires skill in maintaining facet alignment and angle consistency. A poorly executed brillianteering stage, with off-centre star facets or misaligned girdle facets, will receive a lower symmetry grade on the GIA report (GIA Diamond Grading documentation; Reinitz et al., 2006, op. cit.).
Primary sources
GIA Diamond Grading documentation. gia.edu/diamond-grading. Gemological Institute of America. [Cut grade system; proportion parameters; polishing and symmetry assessment; planning methodology context.]
GJEPC (Gem and Jewellery Export Promotion Council). gjepc.org, Mumbai. [India cutting industry data; Surat manufacturing statistics; export figures.]
Reinitz, I. et al. (2006). "Development of the GIA Diamond Cut Grading System." Gems & Gemology, 42(3), GIA. [Cut grade system basis; proportion parameters and their effect on light performance.]
Sarine Technologies product documentation. sarine.com. [Galaxy family scanning instruments; planning software; mapping of inclusions and proportions for yield optimisation.]