There is something called the Fraction System. Here you need to be careful also and make sure you are getting exactly what you are paying for.
You look at a diamond and the tag states it is a 3/4 carat diamond. Looks fine and the price seems right. However the FTC allows jewelers to “round off” diamond weights and guess in what direction they round them off!
A diamond labeled as a 3/4 carat weight diamond may actually weigh anywhere between .69 and .81 carats. This can be a lot of money as,apart from anything else, the price of a diamond leaps up exponentially with the increase in weight. For example you might buy a diamond that has been ’rounded down’ to .69 carats when it is advertised as .75 carats (3/4 carat). If a diamond of G/VS2 is worth about 2,100 dollars but you bought a diamond you thought was .75 carats and paid 3000 dollars you will have lost 900 dollars. Imagine your surprise when you come to get the stone valued at some date in the future!
You need to get in writing the exact weight of the center diamond and if they profess being unable to do so then I suggest you leave the store and go elsewhere.
Many dealers will give an in house appraisal of a diamond they are selling. You don’t hire a fox to guard the hen house and you don’t expect to get an appraisal in your favor from the dealer selling, you a diamond. In all cases you should get an appraisal from an independent gemologist or appraiser.
Some diamonds have flaws and you should ask a jeweler to take a diamond out of a setting to show you the underside or the area when the prongs hold the diamond in place as that will be where any flaws are present. You might consider a small flaw does not matter but it does when it comes to the value and the price of the diamond. Diamonds in rings sometimes turn and that sudden black spot you notice is not new but was previously hidden by the Claws or prongs.
For Part 3 go to Buy Genuine Diamonds - Part 3