Gold Diamond Antique

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Carat Weight
The weight of a diamond is measured in Carats. 1 Carat equals 0.2 gram and there are 100 points to a carat. Thus a 50 point diamond is half a carat (0.50ct) and weights 0.1 gram. A Grain, no longer used, is accepted to be 0.050 grams. Many dealers still use the terms a grainer meaning 0.25ct, two grainer - half carat, six grainer- 1.5 carats etc.

There is an approximate relationship between weight and diameter of a round brilliant cut diamond. This is useful when trying to estimate the size of a diamond.

Weight: Size (diameter): Weight: pts (diameter): Weight: fractions
0.05ct 1.00mm 5pts 1/20th
0.10ct 3.00mm 10pts 1/10th
0.20ct 3.85mm 20pts 1/5th
0.25ct 4.10mm 25pts 1/4
0.33ct 4.55mm 33pts 1/3rd
0.40ct 4.80mm 40pts
0.50ct 5.15mm 50pts 1/2
0.66ct 5.72mm 66pts 2/3
0.75ct 6.00mm 75pts 3/4
0.90ct 6.40mm 90pts
1.00ct 6.65mm 100pts 1 carat
1.50ct 7.50mm 150pts 1 1/2
2.00ct 8.10mm 200pts 2 carats

Diamond Weight Groups

Diamond prices are grouped in to internationally accepted ranges and used throughout the world. The price steps for polished round brilliant cuts are as follows:
From
To
From
To
  0.01ct 0.03ct   0.50ct 0.69ct
  0.04 0.07   0.70 0.89
  0.08 0.14   0.90 0.99
  0.15 0.17   1.00 1.49
  0.18 0.22   1.50 1.99
  0.23 0.29   2.00 2.99
  0.30 0.37   3.00 3.99
  0.38 0.45   4.00 4.99
  0.46 0.49   5.00 5.99