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Diamonds « Back to Education

  • DIAMONDS

    DIAMONDS

        
    • History
    • A Brief History
    • Diamond Cutting
    • Famous Diamonds
    • Budget
    • Shape
    • Four Cs
    • Cut

      The Most Important C

      Cut is considered by many to be the most important "C". Only when precisely calculated planes and angles are used, does the stone achieve its greatest possible beauty. A badly cut diamond, no matter how good its color and clarity will not match the fire and brilliance of a better-cut diamond with comparatively lower color and clarity.

      Diamond Cut Diagram
      Experts express differing opinions on the best table size (the diameter of the largest facet on the top of the stone) and the best depth for a diamond, because these factors alone are not sufficient to accurately judge its cut.

      Other factors - crown angle, girdle thickness, pavilion depth-percentage (the ratio of depth to girdle diameter), culet size, polish and symmetry - also play a role in judging a diamond's overall cut quality.

      Light Emission

      A well-cut diamond will reflect most of the light back to the observer's eye. A poorly cut diamond will reflect only a small proportion of the light that enters it.
      Diamond Light Emission Diagram


      Diamond Cut guides

      We at Gemnation use the following data tables as a guideline to understanding cut grades for brilliant diamonds. Round diamonds are the only shape that can be realistically evaluated with these measures. Other shapes, however, are also dependent on other factors and mere mathematical formulae will not necessarily determine a diamond's magnficence.

      The data presented here is a composite of information from a multitude of sources, including definitions of the Tolkowsky Brilliant, Scandinavian Standard Brilliant, Eulitz Brilliant, and the AGS Laboratories' Ideal cut, together with our own gemologists' knowledge and experience.

      Round

       
      Premium Ideal

      Ideal

      Excellent

      Very Good

      Good

      Fair

      Poor
      Total Depth %
      59.5 - 61.9
      59.1 - 62.3
      58.5 - 63
      57.5 - 63.5
      57 - 64
      56 - 67
      <56 >67
      Table %
      55 - 57
      53 - 58
      52 - 60
      51.5 - 63
      51 - 65
      50 - 70
      <50 >70
      Symmetry
      VG - EX
      G - EX
      G - EX
      G - EX
      All
      All
      All
      Culet
      None
      None - Med
      None - Sl. Large
      None - Large
      None - Large
      None - Very Large
      None - Extr. Large
      Gridle
      Thin, Med, Sl Thk
      Thin, Med, Sl Thk, Thk
      Thin, Med, Sl Thk, Thk
      Very Thn - Thick
      Very Thn - Very Thick
      Ext Thn - Ext Thick
      Ext Thn - Ext Thick
      Polish
      VG - EX
      G - EX
      G - EX
      All
      All
      All
      All
      Clarity
      SI1 - FL
      SI1 - FL
      All
      All
      All
      All
      All

      Princess

       
      Premium Ideal

      Ideal

      Excellent

      Very Good

      Good

      Fair

      Poor
      Total Depth %
      65 - 70
      63 - 70
      62 - 73
      62 - 75
      56 - 82
      55 - 86
      <55 >86
      Table %
      65 - 72
      65 - 72
      62 - 74
      57 - 78
      55 - 85
      57 - 89
      <57 >89
      Ratio L:W
      1:1 - 1.05:1
      1:1 - 1.15:1
      1:1 - 1.75:1
      1:1 - 1.75:1
      1:1 - 2:1
      1:1 - 2:1
      1:1 - 2:1

      Radiant

       
      Premium Ideal

      Ideal

      Excellent

      Very Good

      Good

      Fair

      Poor
      Total Depth %
      63 - 70
      63 - 70
      63 - 72
      62 - 74
      56 - 78
      55 - 83
      <55 >83
      Table %
      68 - 72
      68 - 72
      67 - 74
      65 - 78
      63 - 80
      53 - 83
      <53 >83
      Ratio L:W
      1:1 - 1.05:1
      1:1 - 1.15:1
      1:1 - 1.75:1
      1:1 - 1.75:1
      1:1 - 2:1
      1:1 - 2:1
      1:1 - 2:1

      Emerald

       
      Premium Ideal

      Ideal

      Excellent

      Very Good

      Good

      Fair

      Poor
      Total Depth %
      61 - 67.5
      61 - 67.5
      61 - 69
      60 - 70
      58 - 75.5
      54.5 - 81
      <54.5 >81
      Table %
      62 - 69
      62 - 69
      62 - 71
      61 - 72
      56 - 75
      55 - 82
      <55 >82
      Ratio L:W
      1.3:1 - 1.4:1
      1.2:1 - 1.75:1
      1.05:1 - 2:1
      1.05:1 - 2:1
      1.05:1 - 2:1
      1.05:1 - 2:1
      1.05:1 - 2:1

      Oval

       
      Premium Ideal

      Ideal

      Excellent

      Very Good

      Good

      Fair

      Poor
      Total Depth %
      59 - 62
      59 - 62
      69 - 63
      57.5 - 65.5
      55 - 69
      46 - 76
      <46 >76
      Table %
      57 - 60
      57 - 60
      54 - 61.5
      52 - 64
      51 - 66
      50 - 71
      <50 >71
      Ratio L:W
      1.4:1 - 1.6:1
      1.35:1 - 1.65:1
      1.3:1 - 1.7:1
      1.1:1 - 1.90:1
      1.1:1 - 1.90:1
      1.1:1 - 1.90:1
      1.1:1 - 1.90:1

      Pear

       
      Premium Ideal

      Ideal

      Excellent

      Very Good

      Good

      Fair

      Poor
      Total Depth %
      59 - 63
      59 - 63
      59 - 64
      58 - 65
      54 - 69
      51 - 73
      <51 >73
      Table %
      57 - 60
      57 - 60
      54 - 62.5
      53 - 64
      51 - 66
      48 - 70
      <48 >70
      Ratio L:W
      1.6:1 - 1.7:1
      1.5:1 - 1.75:1
      1.25:1 - 1.85:1
      1.2:1 - 1.9:1
      1.1:1 - 2.0:1
      1.1:1 - 2.0:1
      1.1:1 - 2.0:1

      Marquise

       
      Premium Ideal

      Ideal

      Excellent

      Very Good

      Good

      Fair

      Poor
      Total Depth %
      59 - 63
      59 - 63
      58 - 64
      57.5 - 65
      54.5 - 69
      50.5 - 75
      <50.5 >75
      Table %
      57 - 60
      57 - 60
      55 - 62
      53 - 64
      51 - 66
      50 - 70
      <50 >70
      Ratio L:W
      1.9:1 - 2.1:1
      1.75:1 - 2.25:1
      1.70:1 - 2.3:1
      1.60:1 - 2.4:1
      1.50:1 - 2.5:1
      1.50:1 - 2.5:1
      1.50:1 - 2.5:1

      Heart

       
      Premium Ideal

      Ideal

      Excellent

      Very Good

      Good

      Fair

      Poor
      Total Depth %
      57 - 59
      57 - 59
      56 - 60
      54 - 60
      51 - 62
      46 - 67
      <46 >67
      Table %
      57 - 60
      57 - 60
      54 - 62
      53 - 64
      51 - 66
      46 - 70
      <46 >70
      Ratio L:W
      0.98:1 - 1.02:1
      0.90:1 - 1.10:1
      0.85:1 - 1.15:1
      0.82:1 - 1.18:1
      0.80:1 - 1.20:1
      0.80:1 - 1.20:1
      0.80:1 - 1.20:1

      Cushion

       
      Premium Ideal

      Ideal

      Excellent

      Very Good

      Good

      Fair

      Poor
      Total Depth %
      59 - 62
      59 - 62
      58 - 64
      57 - 69
      55 - 73
      50 - 80
      <50 >80
      Table %
      57 - 60
      57 - 60
      54 - 62
      52 - 65
      51 - 67
      48 - 72
      <48 >72
      Ratio L:W
      1:1 - 1.05:1
      1:1 - 1.10:1
      1:1 - 1.12:1
      1:1 - 1.15:1
      1:1 - 1.20:1
      1:1 - 1.20:1
      1:1 - 1.20:1

      Trilliant

       
      Premium Ideal

      Ideal

      Excellent

      Very Good

      Good

      Fair

      Poor
      Total Depth %
      40 - 42
      40 - 42
      38 - 44
      37 - 45
      35 - 48
      30 - 54
      <30 >54
      Table %
      58 - 60
      57 - 60
      54 - 62
      52 - 65
      51 - 67
      48 - 72
      <48 >72
      Ratio L:W
      0.98:1 - 1.02:1
      0.95:1 - 1.05:1
      0.92:1 - 1.08:1
      0.90:1 - 1.10:1
      0.88:1 - 1.12:1
      0.88:1 - 1.12:1
      0.88:1 - 1.12:1

      Asscher

       
      Premium Ideal

      Ideal

      Excellent

      Very Good

      Good

      Fair

      Poor
      Total Depth %
      59 - 67
      59 - 67
      59 - 69
      57 - 72
      55 - 75
      50 - 78
      <50 >78
      Table %
      57 - 60
      57 - 60
      53 - 62
      52 - 72
      55 - 75
      50 - 78
      <50 >78
      Ratio L:W
      1:1 - 1.02:1
      1:1 - 1.05:1
      1:1 - 1.05:1
      1:1 - 1.08:1
      1:1 - 1.08:1
      1:1 - 1.08:1
      1:1 - 1.08:1
      In Association with Amazon.com

      Buy Books about Diamonds and Gems

      Gemnation has partnered with Amazon.com to bring you
      the most relevant diamond, gem and ring buying books and guides.
    • Color
    • Clarity
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    • Diamond Marketing
    • What's All The Fuss?
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    WATCHES

        
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    Jewelry

        
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  • GLOSSARY

    GLOSSARY

The Most Important C

Cut is considered by many to be the most important "C". Only when precisely calculated planes and angles are used, does the stone achieve its greatest possible beauty. A badly cut diamond, no matter how good its color and clarity will not match the fire and brilliance of a better-cut diamond with comparatively lower color and clarity.

Diamond Cut Diagram
View diamond parts in more detail.

Experts express differing opinions on the best table size (the diameter of the largest facet on the top of the stone) and the best depth for a diamond, because these factors alone are not sufficient to accurately judge its cut.

Other factors - crown angle, girdle thickness, pavilion depth-percentage (the ratio of depth to girdle diameter), culet size, polish and symmetry - also play a role in judging a diamond's overall cut quality.

Light Emission

A well-cut diamond will reflect most of the light back to the observer's eye. A poorly cut diamond will reflect only a small proportion of the light that enters it.
Diamond Light Emission Diagram


Diamond Cut guides

We at Gemnation use the following data tables as a guideline to understanding cut grades for brilliant diamonds. Round diamonds are the only shape that can be realistically evaluated with these measures. Other shapes, however, are also dependent on other factors and mere mathematical formulae will not necessarily determine a diamond's magnficence.

The data presented here is a composite of information from a multitude of sources, including definitions of the Tolkowsky Brilliant, Scandinavian Standard Brilliant, Eulitz Brilliant, and the AGS Laboratories' Ideal cut, together with our own gemologists' knowledge and experience.

Round

 
Premium Ideal

Ideal

Excellent

Very Good

Good

Fair

Poor
Total Depth %
59.5 - 61.9
59.1 - 62.3
58.5 - 63
57.5 - 63.5
57 - 64
56 - 67
<56 >67
Table %
55 - 57
53 - 58
52 - 60
51.5 - 63
51 - 65
50 - 70
<50 >70
Symmetry
VG - EX
G - EX
G - EX
G - EX
All
All
All
Culet
None
None - Med
None - Sl. Large
None - Large
None - Large
None - Very Large
None - Extr. Large
Gridle
Thin, Med, Sl Thk
Thin, Med, Sl Thk, Thk
Thin, Med, Sl Thk, Thk
Very Thn - Thick
Very Thn - Very Thick
Ext Thn - Ext Thick
Ext Thn - Ext Thick
Polish
VG - EX
G - EX
G - EX
All
All
All
All
Clarity
SI1 - FL
SI1 - FL
All
All
All
All
All

Princess

 
Premium Ideal

Ideal

Excellent

Very Good

Good

Fair

Poor
Total Depth %
65 - 70
63 - 70
62 - 73
62 - 75
56 - 82
55 - 86
<55 >86
Table %
65 - 72
65 - 72
62 - 74
57 - 78
55 - 85
57 - 89
<57 >89
Ratio L:W
1:1 - 1.05:1
1:1 - 1.15:1
1:1 - 1.75:1
1:1 - 1.75:1
1:1 - 2:1
1:1 - 2:1
1:1 - 2:1

Radiant

 
Premium Ideal

Ideal

Excellent

Very Good

Good

Fair

Poor
Total Depth %
63 - 70
63 - 70
63 - 72
62 - 74
56 - 78
55 - 83
<55 >83
Table %
68 - 72
68 - 72
67 - 74
65 - 78
63 - 80
53 - 83
<53 >83
Ratio L:W
1:1 - 1.05:1
1:1 - 1.15:1
1:1 - 1.75:1
1:1 - 1.75:1
1:1 - 2:1
1:1 - 2:1
1:1 - 2:1

Emerald

 
Premium Ideal

Ideal

Excellent

Very Good

Good

Fair

Poor
Total Depth %
61 - 67.5
61 - 67.5
61 - 69
60 - 70
58 - 75.5
54.5 - 81
<54.5 >81
Table %
62 - 69
62 - 69
62 - 71
61 - 72
56 - 75
55 - 82
<55 >82
Ratio L:W
1.3:1 - 1.4:1
1.2:1 - 1.75:1
1.05:1 - 2:1
1.05:1 - 2:1
1.05:1 - 2:1
1.05:1 - 2:1
1.05:1 - 2:1

Oval

 
Premium Ideal

Ideal

Excellent

Very Good

Good

Fair

Poor
Total Depth %
59 - 62
59 - 62
69 - 63
57.5 - 65.5
55 - 69
46 - 76
<46 >76
Table %
57 - 60
57 - 60
54 - 61.5
52 - 64
51 - 66
50 - 71
<50 >71
Ratio L:W
1.4:1 - 1.6:1
1.35:1 - 1.65:1
1.3:1 - 1.7:1
1.1:1 - 1.90:1
1.1:1 - 1.90:1
1.1:1 - 1.90:1
1.1:1 - 1.90:1

Pear

 
Premium Ideal

Ideal

Excellent

Very Good

Good

Fair

Poor
Total Depth %
59 - 63
59 - 63
59 - 64
58 - 65
54 - 69
51 - 73
<51 >73
Table %
57 - 60
57 - 60
54 - 62.5
53 - 64
51 - 66
48 - 70
<48 >70
Ratio L:W
1.6:1 - 1.7:1
1.5:1 - 1.75:1
1.25:1 - 1.85:1
1.2:1 - 1.9:1
1.1:1 - 2.0:1
1.1:1 - 2.0:1
1.1:1 - 2.0:1

Marquise

 
Premium Ideal

Ideal

Excellent

Very Good

Good

Fair

Poor
Total Depth %
59 - 63
59 - 63
58 - 64
57.5 - 65
54.5 - 69
50.5 - 75
<50.5 >75
Table %
57 - 60
57 - 60
55 - 62
53 - 64
51 - 66
50 - 70
<50 >70
Ratio L:W
1.9:1 - 2.1:1
1.75:1 - 2.25:1
1.70:1 - 2.3:1
1.60:1 - 2.4:1
1.50:1 - 2.5:1
1.50:1 - 2.5:1
1.50:1 - 2.5:1

Heart

 
Premium Ideal

Ideal

Excellent

Very Good

Good

Fair

Poor
Total Depth %
57 - 59
57 - 59
56 - 60
54 - 60
51 - 62
46 - 67
<46 >67
Table %
57 - 60
57 - 60
54 - 62
53 - 64
51 - 66
46 - 70
<46 >70
Ratio L:W
0.98:1 - 1.02:1
0.90:1 - 1.10:1
0.85:1 - 1.15:1
0.82:1 - 1.18:1
0.80:1 - 1.20:1
0.80:1 - 1.20:1
0.80:1 - 1.20:1

Cushion

 
Premium Ideal

Ideal

Excellent

Very Good

Good

Fair

Poor
Total Depth %
59 - 62
59 - 62
58 - 64
57 - 69
55 - 73
50 - 80
<50 >80
Table %
57 - 60
57 - 60
54 - 62
52 - 65
51 - 67
48 - 72
<48 >72
Ratio L:W
1:1 - 1.05:1
1:1 - 1.10:1
1:1 - 1.12:1
1:1 - 1.15:1
1:1 - 1.20:1
1:1 - 1.20:1
1:1 - 1.20:1

Trilliant

 
Premium Ideal

Ideal

Excellent

Very Good

Good

Fair

Poor
Total Depth %
40 - 42
40 - 42
38 - 44
37 - 45
35 - 48
30 - 54
<30 >54
Table %
58 - 60
57 - 60
54 - 62
52 - 65
51 - 67
48 - 72
<48 >72
Ratio L:W
0.98:1 - 1.02:1
0.95:1 - 1.05:1
0.92:1 - 1.08:1
0.90:1 - 1.10:1
0.88:1 - 1.12:1
0.88:1 - 1.12:1
0.88:1 - 1.12:1

Asscher

 
Premium Ideal

Ideal

Excellent

Very Good

Good

Fair

Poor
Total Depth %
59 - 67
59 - 67
59 - 69
57 - 72
55 - 75
50 - 78
<50 >78
Table %
57 - 60
57 - 60
53 - 62
52 - 72
55 - 75
50 - 78
<50 >78
Ratio L:W
1:1 - 1.02:1
1:1 - 1.05:1
1:1 - 1.05:1
1:1 - 1.08:1
1:1 - 1.08:1
1:1 - 1.08:1
1:1 - 1.08:1
In Association with Amazon.com

Buy Books about Diamonds and Gems

Gemnation has partnered with Amazon.com to bring you
the most relevant diamond, gem and ring buying books and guides.
Email Us Live Chat Call 866-323-8463 Call 718-663-3970

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