Russian grading system for fancy-cut diamonds |
|
|
SQUARE
|
Group
|
А
|
n=Ar/Br
|
1.00 – 1.10
|
br, %
|
Optimal |
60
|
Toler.limits |
±10
|
hr, %
|
Optimal |
2
|
Toler.limits |
±1
|
a
|
Optimal |
40°
|
Toler.limits |
±5°
|
a1
|
Optimal |
24°
|
Toler.limits |
±6°
|
b
|
Optimal |
50°
|
Toler.limits |
±5°
|
b1
|
Optimal |
41°
|
Toler.limits |
±2°
|
b2
|
Optimal |
36°
|
Toler.limits |
±2°
|
|
|
|
PRINCESS
|
n=Ar/Br
|
1,0 - 1,15
|
br, %
|
65 - 75
|
hr, %
|
0,7 - 3,0
|
a
|
35-38°
|
a1
|
29-33°
|
b
|
50-60°
|
b1
|
39-42°
|
|
|
|
TRIANGLE CUT
|
n=Ar/Br
|
1.00 – 1.10
|
br, %
|
60-70
|
hr, %
|
1-5
|
a
|
30-34°
|
a1
|
29-33°
|
b
|
40-42°
|
b1
|
39-43°
|
h Н1
(% from h1)
|
20-40 in plane
|
h КН
(% from hН)
|
80-90
|
h В1
(% from hВ)
|
50-55
|
|
|
Optimal values and tolerance limits br и hr
in % from Br.
|
|
|