Standard Round Brilliant with Vertically Split Mains
GemCad Derived Rendering by Bob Keller
SRB Variation with Vertically Split Mains Angles for R.I. = 1.54 73 facets + 16 facets on girdle = 89 8-fold, mirror-image symmetry 96 index L/W = 1.000 T/W = 0.597 T/L = 0.597 P/W = 0.449 C/W = 0.157 H/W = (P+C)/W+0.02 = 0.626 P/H = 0.717 C/H = 0.251 Vol./W^3 = 0.209 Brightness at 0 degrees tilt for R.I. = 1.54
COS = 42.7% ISO = 56.8%
Pavilion pb 44.50 03-09-15-21-27-33-39-45-51-57-63-69-75-81-87-93 Cut to temporary center point g 90.00 03-09-15-21-27-33-39-45-51-57-63-69-75-81-87-93 Cut to meet pb pm 42.00 01-11-13-23-25-35-37-47-49-59-61-71-73-83-85-95 Cut to meet pb,g Crown cb 42.00 03-09-15-21-27-33-39-45-51-57-63-69-75-81-87-93 Cut to meet g - level girdle cm 38.00 01-11-13-23-25-35-37-47-49-59-61-71-73-83-85-95 Cut to meet cb,g s 22.00 06-18-30-42-54-66-78-90 Cut to meet cm,cb t 0.00 Table Cut to meet s,cm This variation of the SRB doubles the number of main facets from 8 to 16 by splitting them vertically - instead of cutting 1 main facet at 96° as with the classic version, 2 main facets are cut at 95° and 1°, instead of 1 at 12°, 2 at 11° and 13° and so forth. The mains can be split on the pavilion only, crown only, or both. Adding more facets by splitting the mains increases the scintillation and is one way of adapting or scaling the SRB for use with larger stones.
The SRB with Vertically Split Mains Design File is available for GemCad users.