The 4 C's of Diamonds
The value of a diamond is determined by its Cut, Color, Clarity and Carat, also known as the classic "Four C's". Understanding such criteria as diamond grading reports, and the factors effecting a diamond's cost will help the buyer make a confident and sound decision when making a purchase.
The weight of a diamond is generally given in carats. One carat equals 0.2 grams. The weight of small diamonds is frequently expressed in points, with one point equaling 0.01 carats.
As diamonds increase in weight, their size becomes less predictable. Diamonds with a shallow cut can have a greater diameter than a deep cut with the same weight. So if size is important to you, focus on diamond measurements as opposed to carat weight. Diamonds that look big for their weight may have reduced brilliance and fire. An increase in carat weight does not produce the same increase in millimeter diameter. For example, there is a 25% increase in carat weight from 1.00 carats to 1.25 carats but less than 8% increase in diameter (6.5 to 7.0 mm).
Look for diamonds that have a diameter measurement that is at least as large as the average for that carat weight. There is no need to pay for the carat weight you can't see.