Diamond Weight Categories
Diamond Carat Weight
Diamonds are the heaviest and densest material known to man. Diamonds are weighed in carats. A carat is .2 grams. A gram of diamond would be a massive 5 carats. Very large in diamond terms although the actual diamond is small.
A carat is further divided into Points, and there are 100 Points to a carat. So 1 point is .002 of a gram. Very small indeed.
There is a scale of weight for Diamonds and this is shown here:
| Weight |
Size (diameter) |
Weight: pts (diameter) |
Weight: fractions |
| 0.10ct |
3.00mm |
10pts |
1/10th |
| 0.20ct |
3.85mm |
20pts |
1/5th |
| 0.05ct |
1.00mm |
5pts |
1/20th |
| 0.25ct |
4.10mm |
25pts |
1/4th |
| 0.33ct |
4.55mm |
33pts |
1/3th |
| 0.40ct |
4.80mm |
40pts |
4/10ths |
| 0.50ct |
45.15mm |
50pts |
1/2th |
| 0.66ct |
5.72mm |
66pts |
2/3th |
| 0.75ct |
6.00mm |
75pts |
23/4th |
| 0.90ct |
6.40mm |
90pts |
9/10ths |
| 1.00ct |
6.65mm |
100pts |
1 carat |
| 1.50ct |
7.50mm |
150pts |
1&1/2 carats |
| 2.00ct |
8.10mm |
200pts |
2 carats |
Due to the minute differences in the weight of most diamonds they should always be accurately weighed on an electronic scale to the nearest 1000th of a carat (.001). Stones are always rounded up or down to the nearest 1000th of a carat by the way.
The other factor to consider with weight is a certificate. Where a diamond has been assessed and weighed at a laboratory, a certificate should be issued to confirm the assessment. No stones should ever be purchased without a certificate from a bona fide laboratory.
| Code |
Laboratory |
| ADL |
Antwerp Diamond Laboratory |
| AGA | American Gem Apraisal Laboratories |
| CIB | CIBJO (Europe) |
| CSA | Jewellery Council of South Africa |
| DGL | Diamond Grading Laboratories (London) |
| EGI | European Gemmological Institute (Antwerp) |
| EGL | European Gemmological Institute (Antwerp & London) |
| PNF | P N Ferstenberg Pbv A |
| GAG | Gesellschaft fur Angewandte Gemmologie |
| GAN | Gemological Institute of Antwerp |
| GIA | Gemological Institute of America |
| GII | National Gemological Institue of Israel |
| GIL | Gem Information Laboratory |
| GTL | Gem Testing Laboratory of Great Britain |
| NGL | Northern Gemmological Laboratories (UK) |
| HRD | Diamond High Council (Antwerp) |
| HRG | Heinz R Gartner, DGemG, FGA (Germany) |
| IGI | International Gemmological Institute (Antwerp) |
| PSL | Precious Stone Laboratory (London) |
| VPT | Verena Pagel-Theisen, DGemG FGA (Germany) |
| WG | Werner Galia, DGem, (Germany) |
It cannot be iterated enough to ensure that all diamonds you buy should have a certificate from one of the above laboratories.
See also Diamond Appraisal
More information on carat weight can be obtained here Weight of Diamonds
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