Can someone please explain the diamond "point" system to me?

[the_universe]

with regards to tiny diamonds what does it mean when someone wants a 1 pointer or .5 pointer? More specifically in this chart found here:
http://www.walshbrothers.co.uk/Update/dia04.htm

how come 1.7 mm diamond is lower in points than a 1.5 mm; 1 point vs 1.5 points respectively. Is it a typo?

thank you

 

[chrono]

Re: Can someone please explain the diamond "point" system to

There is a typo in the chart; I believe it is supposed to be a 2 pointer.

 

[drk14]

Re: Can someone please explain the diamond "point" system to

1 carat = 100 points.
1 point = 0.01 carat.

The chart has a few typos. For example, the "1" in the fourth row of the "Points" column should be a "2". Also, "Milimeters" in the label of the first column should be "Millimeters".

 

[HopeDream]

Re: Can someone please explain the diamond "point" system to

Typos aside,

Diamonds are sold by weight, but they are also tiny, so we use a different system of weight units that scales well to tiny things.

1 point = 2 milligrams
1 carat = 100 points = 200 milligrams = 0.2 grams

1ml of water weighs 1 gram, a small paperclip also often weighs about a gram.
A one carat diamond weighs about the same as 1/5 of a paperclip.

The shape that the same amount of diamond material is in will change the face up size of the gem. It's really all about geometry: rounds tend to face up larger than asschers, because rounds are kind of like cones, vs asschers which are more like square pyramids. Some diamonds carry their weight more spread out (marquise)and so face up larger, and others carry their weight more compactly (asschers) and so face up smaller.

It's kind of like if you have a square of tinfoil laid out flat and you look at it from the top down it will appear to be one size, but if you crumple the tinfoil up, and then look at it again from the top down it will look a smaller size.

 

[pyramid]

Re: Can someone please explain the diamond "point" system to

100 points = 1 carat
75 points = 0.75 carat or three quarters of a carat
66 points = 0.66 carat or two thirds of a car
50 points = 0.50 carat or half carat
33 points = 0.33 carat or third of a carat
20 points = 0.20 carat or one fifth of a carat
25 points = 0.25 carat or quarter of a carat
15 points = 0.15 carat
10 points = 0.1 carat
1 point = 0.01 carat
half of a point = 0.005 carat
quarter of a point = 0.0025 carat

 

[Sunstorm]

Re: Can someone please explain the diamond "point" system to

Yes there are typos others mentioned, I also wanted to add that the points do not correlate to millimeters and the increase is not linear; take for example that a 1 mm stone is generally half a point 0.005 carats and a 1.2 mm stone is about 0.008 carats. More often than not we use these sizes in halos to get a nice proportional look, for 1.2 mm stones the jeweler has to set the stones very tight so we do not get bulky halos.

 

[Andelain]

Re: Can someone please explain the diamond "point" system to

100 points = 1 carat
75 points = 0.75 carat or three quarters of a carat
66 points = 0.66 carat or two thirds of a car
50 points = 0.50 carat or half carat
33 points = 0.33 carat or third of a carat
20 points = 0.20 carat or one fifth of a carat
25 points = 0.25 carat or quarter of a carat
15 points = 0.15 carat
10 points = 0.1 carat
1 point = 0.01 carat
half of a point = 0.005 carat
quarter of a point = 0.0025 carat

How do you divide up the tires when you have 2/3 of a car?

 

[cflutist]

Re: Can someone please explain the diamond "point" system to

To further confuse you, a "grain" is .25 cts or 25 points.
Therefore a 4 "grainer" is 1 ct.