Standard Round Brilliant with Horizontally Split Mains
GemCad Derived Rendering by Bob Keller Bob Keller

SRB Variation with Horizontally Split Mains
SRB Variation with Horizontally 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 = 0.528 T/L = 0.528 P/W = 0.487 C/W = 0.172 H/W = (P+C)/W+0.02 = 0.680 P/H = 0.717 C/H = 0.253
Vol./W^3 = 0.227 Brightness at 0 degrees tilt for R.I. = 1.54
COS = 34.7% ISO = 38.2%
Pavilion
pb 47.00 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
pm1 45.00 96-12-24-36-48-60-72-84 Cut to meet pb,g
pm2 43.00 96-12-24-36-48-60-72-84 Cut to meet pb, pm1
Crown
cb 47.00 03-09-15-21-27-33-39-45-51-57-63-69-75-81-87-93 Cut to meet g - level girdle
cm1 38.00 96-12-24-36-48-60-72-84 Cut to meet cb,g
cm2 34.00 96-12-24-36-48-60-72-84 Cut to meet cb,cm1
s 25.00 06-18-30-42-54-66-78-90 Cut to meet cb,cm1,cm2
t 0.00 Table Cut to meet s,cm2
This variation of the SRB doubles the number of main facets from 8 to 16 by splitting them horizontally with the pairs of mains cut at the same index but different angles. 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.


Index of Gem Designs

Perfect Transfer Index

Table of Contents


© Bob's Rock Shop Bob Keller