Russian grading system for fancy-cut diamonds

SQUARE

Group

À

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 Í1
(% from h1)

20-40 in plane

h ÊÍ
(% from hÍ)

80-90

h Â1
(% from hÂ)

50-55

Optimal values and tolerance limits br è hr in % from Br.