How to Buy a Diamond

Buying a diamond is one of the most expensive purchases you will make,the same as buying a watch,such as Rolex,Richard Mille,U-Boat and Porsche Design. This diamond buying guide explains how to get the highest quality diamond for your money as well as how to care for your diamonds. We also teach you about diamond treatments and how to protect yourself.
4C's of Diamond Quality
Diamonds are graded by four characteristics: cut, carat (weight), clarity, and color. All four of these properties determine how much a diamond is worth.
Cut - What is the proportion of the diamond? Round brilliant diamonds are commonly cut with 58 facets. The better proportioned these facets are on the diamond, the more light will be reflected back to the viewer's eye. This is extremely important. When cut properly, the diamond will sparkle more. Diamond cuts are measured by the table percentage, so always ask for it. A good table percentage is between 55-60%. Cut also refers to the shape such as: round, pear, and oval. If you are having a diamond mounted, write down the measurements of your stone. Measurements never change. Measure the stone after it is mounted and verify that it matches the appraisal and/or certificate.
Carat - How big is the diamond? Larger diamonds often cost more per carat due to their size. There are 100 points to a carat. Hence a 50 point diamond is 1/2 a carat. (There are 5 carats to a gram.) Always get the actual point size of a diamond rather than a fractional weight. Sometimes jewelers will try to sell a .90 diamond as a 1 carat diamond. A .90 diamond should be substantially less expensive.
Clarity - How clear is the stone? Clarity ranges from flawless (perfect) to I (included). Here is a chart:
Flawless: perfect inside and out Internally Flawless: may have minor blemishes on the outside VVS1, VVS2: have very very small inclusions. VVS1 inclusions can only be seen through the pavilion. VVS2 inclusions are more visible. VS1, VS2: have very small inclusions. VS1 inclusions are harder to see than VS2. SI1, SI2, SI3: have small inclusions I1, I2, I3: have inclusions visible to the naked eye
Color: Diamond colors generally range from D - X for white and yellow diamonds. D is the whitest. Around S they become "Fancy" yellow Diamonds. One can also find green, pink, red, blue and brown diamonds - though these are usually irradiated.
Be certain to ask: Do you guarantee the color and clarity of your stones? Many states allow dealers to be off by one color and/or one clarity.
Also there are some watches with diamond on them,such as Rolex Datejust,Rolex Day-Date,Rolex Prince,Breitling and Bell&Ross,also you can check the diamonds with the methods provided below.