PentaRound
GemCad Ray Traces for RI = 1.62
Random Model Cosine Model ISO Model
PentaRound
Designed by Bob Keller - November 2001 Bob Keller
For Topaz, Tourmaline, Garnet, Spinel, Corundum
Angles for R.I. = 1.62 56 facets + 20 facets on girdle = 76
5-fold, mirror-image symmetry 120 index
L/W = 1.000 T/W = 0.553 T/L = 0.553 P/W = 0.429 C/W = 0.174 H/W = (P+C)/W+0.02 = 0.623 P/H = 0.689 C/H = 0.279
Vol./W^3 = 0.204 Brightness at 0 degrees tilt for RI = 1.62 COS = 80.8 ISO = 88.7
Pavilion
1 41.00 003-009-015-021-027-033-039-045-051-057
063-069-075-081-087-093-099-105-111-117
Cut to centerpoint - make culet
g1 90.00 003-009-015-021-027-033-039-045-051-057
063-069-075-081-087-093-099-105-111-117
Match 1 - make level girdle
Crown
a 36.47 003-021-027-045-051-069-075-093-099-117 Match g1, establish upper gridle line
b 40.00 009-015-033-039-057-063-081-087-105-111 Match g1.a.g1
c 35.26 002-022-026-046-050-070-074-094-098-118 Meet a.g1.g1.a
d 31.01 120-024-048-072-096 Meet c.a.b
t 0.00 Table Meet d.c.a.b

A PentaRound Design File is available for GemCad users.


Index of Gem Designs

Perfect Transfer Index

Table of Contents


© Bob's Rock Shop Bob Keller